Seerah of Prophet Muhammad 71 - Letters to various Rulers - Dr. Yasir Qadhi | 6th November 2013
Seerah of Prophet Muhammad 71 - Letters to various Rulers - Dr. Yasir Qadhi | 6th November 2013
We will discuss the letters and emissaries the Prophet PBUH sent to various rulers after Khaybar. Note these letters were not sent all at the same time. Rather there are various letters that have sent - some scholars have documented over 25 letters that the Prophet PBUH sent. And indeed each letter is not worth an entire lecture in and of itself, therefore typically, scholars have dedicated one chapter roughly after Khaybar on all the letters the Prophet PBUH sent (but keep in mind these letters were sent at different times to various rulers). The main thing is what lessons we can draw from the letters. Why is it discussed right now? Because it was around this time after Hudaybiyyah, probably even a little bit before Khaybar, were the letters began.
The Letter to Najashi
The first letter was the letter to Najashi. The Prophet PBUH sent him a letter around this time. This is not to be confused with Ja'far's dialogue. That happened over 10 years ago. The letter most likely came when Ja'far left Abyssinia. And the Prophet PBUH sent him a letter and told him, "From Muhammad ibn Abdullah to Najashi the Emperor." And the Prophet PBUH informed him the Islamic belief about Isa AS: "I believe Isa AS is the Messenger of Allah, His ruh." And he said, "Accept Islam and you will be safe," and he concluded the letter with a verse from Surah Ali-Imran, "O People of the Book, come to terms that are common between us (that we worship Allah Alone, and that we don't take ourselves as gods besides Allah)." And this was clearly the most successful of all his letters, because as we know, he accepted Islam. There is some ambiguity as to when he accepted Islam. Many assume it was when Ja'far gave him dawah. But the fact is, if he embraced Islam back then, why would the Prophet PBUH send him a letter now 10 years later, after Hudaybiyyah? Thus it seems to be the case that Najashi was open and interested to Islam, but not fully a Muslim. And it's also interesting that at the end of the letter to Najashi, the Prophet PBUH did not write a threat that, "If you don't accept [Islam], all of your people their sins will be on you." Whereas in the letter to the Emperor of Rome and Persia, both of them got this dire warning that, "If you don't accept, then you shall carry the burden of all of your people on the Day of Judgement." Whereas Najashi seems to have been spared this particular clause. Why? Because the Prophet PBUH most likely knew he was very close to Islam anyway.
According to al-Tabari, Najashi sent his own son, Arha ibn As'hama (أرهى بن أصحمة) (Najashi is only a title; his name was As'hama) with 60 other delegates to Madinah to give the Prophet PBUH gifts and announce Islam. And he said, "If you want, I will come to Madinah." But according to al-Tabari, the two boats drowned and this delegation never arrived. But the Islam of Najashi was known to the Prophet PBUH. So 2.5 years later (9 AH), when Najashi passed away, the Prophet PBUH announced to the sahaba on the very morning that he passed away, "Your brother has died in Abyssinia. Let us pray janazah for him." So the one and only time in the life of the Prophet PBUH janazah was prayed without a body being present was for Najashi. And this leads to the whole controversy in fiqh: When is janazah ala al-ghayb prayed? And the correct opinion appears to be: When a person dies and nobody prays janazah where he died.
The actual letter reported by Ibn al-Qayyim:
"In the Name of Allah, the Most Beneficent, the Most Merciful. From Muhammad the Messenger of Allah to Negus, King of Abyssinia (Ethiopia). Peace be upon him who follows true guidance. Salutations. I entertain Allah's praise, there is no god but He, the Sovereign, the Holy, the Source of peace, the Giver of peace, the Guardian of faith, the Preserver of safety. I bear witness that Jesus, the son of Mary, is the spirit of Allah and His Word which He cast into Mary, the virgin, the good, the pure, so that she conceived Jesus. Allah created him from His spirit and His breathing as He created Adam by His Hand. I call you to Allah Alone with no associate and to His obedience and to follow me and to believe in that which came to me, for I am the Messenger of Allah. I invite you and your men to Allah, the Glorious, the All-Mighty. I hereby bear witness that I have communicated my message and advice. I invite you to listen and accept my advice. Peace be upon him who follows true guidance."
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The Letter to Heraclius the Emperor of Rome
The second most famous letter is that to Caesar, the Emperor of Rome. This letter is recorded in Bukhari and Muslim - fully authentic. Who is the Caesar of the the Prophet's PBUH time? It was Heraclius, who reigned from 610 to 641 CE. He was the emperor of Rome and he was by and large viewed in a favorable light by both Muslims and non-Muslims historians. He has a glorious reign and is credited with major victories especially against the Persians, the Sassanids. (Of course Surah al-Rum predicted this as we discussed during Badr. That the Romans suffered a great defeat at the hands of the Persians: The Persian Emperor Khosrow had launched an attack against the Romans which lasted 15-20 years. With this he managed to conquer most of Iraq, Syria, and even Damascus and Jerusalem. So the Persians conquered Damascus and all these lands, including parts of Egypt. And it seemed the Roman empire was on it lasts legs, but then Allah revealed Surah al-Rum that, "In a FEW years the Romans will gain the upper hand." [see Quran, 30:1-4] When this verse came down, they were on the brink of extinction; but Heraclius regrouped his troops, regained almost all of these lands right up until 628 CE - he reached the capital of the Sassanid Empire, Ctesiphon. And eventually Khosrow has to flee for his life; he died a few days later and Khosrow's son takes over. And he died 27th Feb 628 CE, the 7th year of the Hijrah. This is all happening when the Prophet PBUH is alive.)
Heraclius was a scholar of Christianity. And Christian sources mention many incidents which back this up. The most famous issue of theology was that he tried to unify the two major factions of Christianity of his time: the Monophysites and Dyophysites. This was 1500 years ago. And Caesar tried to combine both strands of Christianity, and in doing so, he brought forth a new theology that was in between the two. He tried to compromise to allow both groups to unite. But he clearly was not a skilled theologian, since there is NO compromise when it comes to theology; so his new theology was not accepted by either group. And the whole issue was over 'Jesus Christ - is he man or God?' And this was the primary question for the first 400-500 years after Isa AS 'died.' So Heraclius tried to bring forth a new theology and it lasted for a while but died away.
As for the letter of the Prophet PBUH to Heraclius, it's mentioned in a lot of detail. The Prophet PBUH sent Dihyah al-Kalbi (دحية الكلبي) to Bosra (where the Quraysh would go to trade). So the Prophet PBUH sent a letter to the governor of Bosra so that he would send it to the Caesar. And it so happened Heraclius was visiting Jerusalem at the time anyway. So the Prophet PBUH sent a letter through Bosra and because Caesar was in Jerusalem which is close by, it arrived to him quickly. And here we begin the narration that Abu Sufyan narrates in Bukhari, the conversation between Abu Sufyan and Heraclius. We went over this in detail before. Abu Sufyan narrates he was trading in Syria in Bosra when a crier comes out and says, "You are being called to Jerusalem." He doesn't know what is going on but lo and behold he is being called to the presence of the emperor himself. And this is an amazing story. Abu Sufyan, from Quraysh, is standing in the palace of Caesar, in front of the emperor himself. And Caesar calls his delegates, an Arab translator, and then poses questions to Abu Sufyan (who then was not yet a Muslim). And Abu Sufyan is there with his group as well. So Heraclius asks all the Arabs present: "Who is the closest to you to this man claiming to be a prophet?" So Abu Sufyan says, "I am." So Heraclius says, "Sit in front of me." This is amazing - it shows us Heraclius's wisdom. He knows these people are enemies to the Prophet PBUH and are still pagan. So how do you extract information from an enemy and prove it to be correct? Look at Heraclius's tactic; and this clearly shows this was a wise and an intelligent ruler - he used them against themselves. He divided the group between Abu Sufyan in the front, and the rest of his colleagues at the back. He says to Abu Sufyan, "I will ask you questions" and he says to the group behind him, "If he lies, motion to me." So Abu Sufyan was forced to tell the whole truth. He knows if he lies, someone will snitch on him. Later when he narrates this story, he said, "Wallahi, had it not been that I was afraid that my companions would accuse me of lying, I would have not spoken the truth." Note, Abu Sufyan is still a pagan at this time.
So Heraclius asks, "What is his family status amongst you?"
Abu Sufyan replied, "He belongs to a good (noble) family amongst us."
Heraclius further asked, "Has anybody amongst you ever claimed the same (i.e. to be a prophet) before him?"
Abu Sufyan replied, "No."
He said, "Was anybody amongst his ancestors a king?"
Abu Sufyan replied, "No."
Heraclius asked, "Do the nobles or the poor follow him?"
Abu Sufyan replied, "It is the poor who follow him."
Heraclius asked, "Are (the numbers of) his followers increasing or decreasing (day by day)?"
Abu Sufyan replied, "They are increasing."
He then asked, "Does anybody amongst those who embrace his religion become displeased, and renounce the religion afterwards?"
Abu Sufyan replied, "No."
Heraclius said, "Have you ever accused him of telling lies before his claim (to be a prophet)?"
Abu Sufyan replied, "No. "
Heraclius said, "Does he break his promises?"
Abu Sufyan replied, "No. We are at truce with him, but we do not know what he will do in it." (And later when Abu Sufyan narrates this story, he said, "I could not find opportunity to say anything against the Prophet PBUH except that.")
Heraclius asked, "Have you ever had a war with him?"
Abu Sufyan replied, "Yes."
Then he said, "What was the outcome of the battles?"
Abu Sufyan replied, "Sometimes he was victorious and sometimes we were victorious."
Heraclius said, "What does he order you to do?"
Abu Sufyan said, "He tells us to worship Allah and Allah Alone, and to not worship anything that our forefathers used to worship. And he orders us to pray, to speak the truth, to be chaste, and to keep good relations with our kith and kin."
Heraclius then explained all of his questions: "I asked you about his family, and your reply was that he belonged to a very noble family. In fact all the apostles come from noble families in their peoples. I questioned you whether anybody else amongst you claimed to be a prophet before, your reply was in the negative. If the answer was in the affirmative, I would have thought that this man was following the previous man's statement (i.e. following a fad and was just trying to be a prophet to be 'cool'). Then I asked you whether anyone of his ancestors was a king. Your reply was in the negative, and if it had been in the affirmative, I would have thought that this man wanted to take back his ancestral kingdom." I further asked whether he was ever accused of telling lies before he said what he said, and your reply was in the negative. So I wondered how a person who does not tell a lie about money (or gold or silver) could ever tell a lie about Allah." (Note this is amazing. Heraclius the kafir is giving 'dawah' to Abu Sufyan the mushrik.) He continues, "I then asked you whether the rich people follow him or the poor. You replied that it was the poor who follow him. And in fact, all of the prophets of God, the poor accepts their message before the rich." (And again, this is a given - anything that attracts the elite and the rich, something is wrong. The truth is always accepted by those who have nothing. The rich and powerful have the most to lose by the truth.) He continues, "Then I asked you whether his followers were increasing or decreasing. You replied that they were increasing; and this too is the sign of the truth - the truth always gains more followers. I further asked you whether there was anybody, who, after embracing his religion, became displeased, and discarded his religion. Your reply was in the negative, and in fact this is (the sign of) true faith when its delight enters the hearts and mixes with them completely. I asked you whether he had ever betrayed. You replied in the negative; and the prophets of God can never betray or break a promise. Then I asked you what he ordered you to do. You replied that he ordered you to worship Allah and Allah Alone, and not to worship any thing along with Him, and forbade you to worship idols, and ordered you to pray, to speak the truth, and to be chaste. If what you have said is true, he will very soon occupy this place underneath my feet; and we knew from our scriptures that God would be sending somebody, but we did not expect it to be from your race (Arabs)." (Subhan'Allah, they were expecting a final prophet but not from the Arabs.) And he continues, "If I could reach him, definitely I would go immediately to meet him; and if I were with him, I would certainly wash his feet." Heraclius then asked for the letter addressed by Allah's Apostle.
The letter reported by al-Tabari:
"In the name of God, the Beneficent, the Merciful: From Muhammad son of Abdullah to Heraclius the Great of the Romans. Peace be upon him, he who follows the right path. Furthermore; I invite you to submit your will to God; submit your will to God and you will be safe, and God will double your reward, and if you reject, you bear the sins of the الأريسيِّين/al-Arisiyin.
قُلْ يَا أَهْلَ الْكِتَابِ تَعَالَوْا إِلَىٰ كَلِمَةٍ سَوَاءٍ بَيْنَنَا وَبَيْنَكُمْ أَلَّا نَعْبُدَ إِلَّا اللَّهَ وَلَا نُشْرِكَ بِهِ شَيْئًا وَلَا يَتَّخِذَ بَعْضُنَا بَعْضًا أَرْبَابًا مِّن دُونِ اللَّهِ ۚ فَإِن تَوَلَّوْا فَقُولُوا اشْهَدُوا بِأَنَّا مُسْلِمُونَ
'And People of the Scripture! Come to a word common to you and us that we worship none but God, and that we associate nothing in worship with Him, and that none of us shall take others as lords beside God. Then, if they turn away, say: Bear witness that we are Muslims.'" [3:64]
[Sidenote: الأريسيِّين (al-Arisiyin) is a word that has caused problems for our classical scholars, because it's not an Arabic word. Most scholars have interpreted 'Arisiyin' to mean the 'peasants' i.e. the 'common folk.' But more on this later.]
Abu Sufyan then added, "When Heraclius had finished his speech and had read the letter, there was a great hue and cry in the Royal Court. And we were told to leave his gathering. I mentioned to my companions as we exited that, 'The matter of Ibn Abi Kabsha (ابن أبي كبشة - a derogatory term they used for Prophet Muhammad) has become so prominent that even the King of Bani al-Asfar (Byzantine) is afraid of him.' Then I started to become sure that he (the Prophet PBUH) would be the conqueror in the near future until I embraced Islam (i.e. Allah guided him to Islam)." So this was the first time Islam firmly entered Abu Sufyan's heart - in the palace of the Caesar. He realized it must be the truth. And there is no question he converted right at the end, but as Allah says, those who converted at the end after the Conquest are not the same as those before [see Quran, 57:10].
We also learn that the Prophet PBUH sent a letter to the Caesar during the Battle of Tabuk. Most likely it was a separate letter, and it could be the same, but we are not sure. And it's mentioned in Musnad Imam Ahmad (not Bukhari) that Heraclius responded to this letter by sending an emissary to the Prophet PBUH. Heraclius found a Christian Arab from the tribe of Tanukh/تنوخ (we don't know his name, but he is called "the One from Tanukh [التنوخي]"). And in seerah literature, this story is called "the Hadith of the Tanukhi (حديث التنوخي)." Heraclius handed a letter to him and said, "I am actually sending you as a lookout. I want you to monitor three things:
1. Does he (the Prophet PBUH) mention the letters that he sends to me and the other kings.
2. Does he mention "the night" when my letter will be read to him - see what his response is.
3. See if he has something strange on his back (Seal of the Prophets).
So the Tanukhi came to the Prophet PBUH; the Prophet PBUH asked him, "Who are you?" he said, "I am a man from Tanukh and the Caesar has sent me." And the Prophet PBUH said, "You should embrace the religion of your forefather Abraham (i.e. become a Muslim)." And the man said, "I will think about it; and here is a letter from Caesar." The Prophet PBUH did not even open the letter, and he just had a conversation with the Tanukhi. And the Tanukhi reports that the Prophet PBUH said, "I sent my letter to Kisra the Emperor of Persia, but he tore it up, so Allah will tear his kingdom up. And I sent my letter to Caesar, and he protected it, so Allah will protect his kingdom." So this is check one (first point). Then the Prophet PBUH opened up the letter and in it the Caesar asked a question: "Your messenger told us your Book mentions a Jannah that is as broad as the skies and the earth [Quran, 3:133]. So if Jannah is as big as the skies and the earth, where then is Jahannam according to your religion?" And the Prophet PBUH responded, "Subhan'Allah, where do you think the night goes when the day comes?" So he PBUH responded with 'layl' i.e. night so this was check two. Then the Tanukhi stayed a day or two waiting to see if he could look at the back of the Prophet PBUH. But eventually he says, "Okay, I'll go back and tell the Caesar I saw two of the three signs," so he went to the Prophet PBUH and said, "O Muhammad, I am leaving now and will go back to the Caesar." But the Prophet PBUH said, "Wait," and he turned around, lowered his shirt, and said, "Go and tell your Caesar what you have seen." So the man returned with all three checks.
In the Western tradition, they do not mention any of these letters, much less the details of the three signs, etc. But from our tradition, we learn that the Caesar then realized that this is true (the Prophet PBUH is a true prophet). Note this story of the Tanukhi is not found in Bukhari. Bukhari actually has 2 stories about the Caesar - you would think it's the same story, but it's not; they are two separate stories. The first of them is the story of Abu Sufyan and Heraclius, and the second of them is Heraclius quizzing his ministers whether to embrace Islam. These stories don't happen the same day. They actually happened maybe a year or two apart. And the second story takes place after the Tanukhi incident. And it goes as follows:
Heraclius was the head of the Christians of Rome. And one of the narrators mentions when he woke up one day, he woke in an angry/sad mood. One of the priests asked him, "Why are you in such a sad mood?" Heraclius said, "I have seen a dream, and my astrologers have foretold a very evil omen/sign. That is, a leader has appeared of a new people [who will challenge me], and these people circumcise themselves." So his ministers/senators said, "What is there to worry about? The only group who practice circumcision are the Jews. So go and send another command, and irritate the Jews (of course antisemitism has always existed among Christianity)" i.e. 'clamp them down.' Before Caesar could enact such a rule, Dihyah al-Kalbi arrived in his court with a message from the Prophet PBUH. And Heraclius said, "Go check is Dihyah circumcised or not." (Now the Arabs by and large did not circumcise themselves. This only began in Islam. Some of them did, some of them didn't, but it certainly was not a custom.) And so Dihyah was examined and lo and behold he is circumcised. And this is what made Heraclius really concerned, so he wrote a letter to his friend (most likely) John IV - and Bukhari does not mention this but one theory (Sh. YQ's theory) is that it is this man who writes the three signs to Heraclius that, "Go test the prophet with these three signs." Then Heraclius sends the Tanukhi with these three signs, and he comes back and all three are checked. So he realizes this is a true prophet.
Now Bukhari continues: When the Tanukhi came back, he called all the senators and says to them, "What do you think if I embrace Muhammad's faith." They start revolting and say, "There's no way you will be our emperor etc." So Heraclius says, "I was just testing your faith. I will never leave Christianity." And so he dies upon his faith, and in fact he dies somewhat of a miserable death in the middle of a coup. He was alive when the Muslims conquered Jerusalem - in less than 7 years, these massive empires were literally conquered by Bedouins from the desert. He sees the carving up of the Roman Empire in his own lifetime. So this is Caesar.
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The Letter to Khosrow the Emperor of Persia
How about the Emperor of Persia? His name was Khosrow. And he had a title of Aparvēz. It's commonly referred to as Parvez in Pakistani and Indian culture of our times. And this Khosrow reigned from 590 to 628 CE and he was the last of the Great Sassanid Kings. After him the Sassanid Empire never regained its glory. He was the final 'great' emperor. After having conquered Damascus, Jerusalem, half of Egypt, etc. he saw his entire empire crumble before his very eyes, and within less than a decade, the Sassanid Empire was wiped off the face of earth as if it never existed. And there's no question this is an amazing event in human history; this mighty civilization and empire which threatened to extinct Rome literally disappears within a few years. And it embraces Islam fully so much so Zoroastrianism is no longer practiced. Historians by and large have painted Khosrow as a very cruel, lustful, sensual emperor. Books mention he had 3000 concubines, and people hated him for his cruelty. And the Prophet PBUH sent him a letter through the ruler of Bahrain. Now Bahrain at the time of the Prophet PBUH wasn't just the island. So the Prophet PBUH sent Abdullah ibn Hudhafah al-Sahmi (عبد الله بن حذافة السهمي) to the ruler of Bahrain to pass on to Khosrow.
Al-Tabari mentions the text of the letter:
"In the Name of Allah, the Most Beneficent, the Most Merciful. From Muhammad the Messenger of Allah to Kisra the King of Persia Peace be upon him who follows true guidance, who believes in Allah and His Messenger, and testifies that there is no god but Allah Alone with no associate, and that Muhammad is His slave and Messenger. I invite you to accept the religion and call of Allah. I am the Messenger of Allah sent to all people in order that I may infuse fear of Allah in every living person, and that the charge may be proved against those who reject the Truth. Accept Islam as your religion so that you may live in security. Otherwise, you will be responsible for all the sins of the Magians (Majus)."
Now Khosrow was very arrogant and he mocked the letter, scoffed at it, and tore up the letter in front of Abdullah ibn Hudhafah. When the news reached back to the Prophet PBUH, the Prophet PBUH said (in Bukhari), "He tore up my letter; Allah will tear his kingdom up *every tearing.*" It's an extra emphasis and indeed this is what happened. The emperor sent a message through one of his governors by the name of Badhan (باذان) - he was a governor of a city more towards Yemen. He said to Badhan, "Send some spies to Madinah and find out more information about this man. If you are able to bring him back physically, then do so." So Badhan chose two of his trusted emissaries, Babawayh (بابويه) and Khur Khasra (خر خسرة), and they went to Madinah with a letter - this was just a ruse, the main mission was to get information about the Prophet PBUH and Islam. And when they arrived in Madinah, they were terrified (because the people knew they were spies). The Prophet PBUH said, "Wait, and come back to me the next day." The next day they came and they brought the letter again - the Prophet PBUH didn't even open it. Rather he said, "Go back to your rabb (Badhan)." Note they called their emperors 'lord' i.e. 'rabb,' So the Prophet PBUH said, "Go back to your rabb and tell him my Rabb has killed his rabb (i.e. Khosrow), and that his son has taken over." Now the two were completely in shock, and they went back to Badhan. By the time they got back, they discovered the news that Khosrow had fled from Ctesiphon, and his son (Shērōē) had executed a coup d'état, and his son sent an army to imprison his own father. In the meantime, his son made a truce with the Romans so they didn't attack; and thus Khosrow's own son killed him a cruel death. Western sources say this happened 28th Feb 628 CE. And this corresponds exactly with when this happened in the seerah, that is Jumada al-Awwal 7 AH. (For those who deny the seerah or hadith, you cannot fabricate this stuff. It's impossible to pinpoint such a thing.) And as the Prophet PBUH predicted, Allah obliterated the Persian Empire within a few years. And such an implosion has never before occurred. Such a huge empire is destroyed. For 350 years the Romans and Persians were at war but none of them vanished. But then within 10 years of the Muslims coming, the Persian Empire was destroyed.
What happened to Badhan? He embraced Islam after realizing what the Prophet PBUH predicted came true, as did the two emissaries who he sent to the Prophet PBUH. The Prophet PBUH then sent them another letter and told them about the rules of jizya. That if anyone accepts Islam, they are a part of the believers; if not, then let them pay the jizya.
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The Letter to Jurayj ibn Mina the Muqawqis of Egypt
There were other letters written. Of the most famous is the letter to the Muqawqis (المقوقس) of Egypt by the name of Jurayj ibn Mina (جريج بن مينا). We don't have in any authentic narration the actual text of the letter, but we do know that the Muqawqis was polite: He sent back gifts, cloth, Duldul (which was to become the mule of the Prophet PBUH), Maria and Sirin, to the Prophet PBUH. The Prophet PBUH is said to have remarked: "The khabith (خبيث) has protected his kingdom (by his politeness), but Allah will not allow his kingdom to last."
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Letters to Other Rulers
And the Prophet PBUH also sent many other letters; notably to Oman after the Conquest of Makkah, and they actually accepted Islam. He also sent letters to other provinces. Scholars have listed over 20 letters. One of them being to Musaylimah al-Kadhdhab (مسيلمة الكذاب) i.e. the Banu Hanifa. And they said, "We will embrace Islam only if you share the power with us." But the Prophet PBUH responded, "Earth belongs to Allah, and Allah will give it to whomever He pleases."
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Benefits of the Letters
1. Long term goals. Most of these letters did not have any immediate major impact. Even Najashi - only he embraced Islam, his people didn't. But there is the clear intention to make the message of Islam a global message. And it's amazing within one decade, every single land he wrote a letter to was within the lands of Islam. It's an amazing reality. So what's happening is the Prophet PBUH is making the Islamic Empire an international empire and nation. It's worthy of dialogue with Caesar, Najashi, Khosrow, etc.
2. Let us notice whom he did not send letters to. There were civilizations beyond Persia, Rome, Abyssinia, etc. There is Africa, China, etc. Why didn't the Prophet PBUH send them any letters? Simple - there is no direct contact with them. There is a pragmatic approach here: concentrate on those that have direct contact with the Muslims and the Arabs.
3. Clearly, the response of the rulers have some type of theological weight for us. Look at what the Prophet PBUH said to Khosrow, "He tore my letter up, Allah will tear his kingdom up." Look at what he said to Caesar, "Because he preserved my letter, Allah will preserve his kingdom." And look at what the Caesar said to Tanukhi, "Does he mention the letters of the kings that he writes to." So clearly there is something theological that we have in our tradition about this regard.
4. Look at the letters themselves: Each letter is very short, succinct, to the point. It's one paragraph. Each begins with 'Bismillah' - this is a sunnah that we should follow in official letters that we write. Each begins 'From so and so to so and so' - this is part of the etiquette that is now standard, and the Prophet PBUH is utilizing it. And each explains the message of Islam in 4-5 sentences. Simple and to the point.
5. Notice as well each letter is catered to the one being written to. They aren't the same. The one written to Najashi is different to that of Caesar. It has the verse of Ali-Imran in it. But the letter to Khosrow doesn't have this verse. Why? He isn't among the People of the Book. In Najashi's case the Prophet PBUH explains Islamic theology regarding Isa AS.
6. Also, when the Prophet PBUH wrote his first letter, he was told, "The emperors do not accept letters from other rulers unless the ruler himself stamps it and seals it with wax." So you have to seal a letter with wax to make it clear that no one has read it. So the Prophet PBUH was told these are the international laws. What did he do? He made a ring for himself and ordered wax to be poured and then he sealed the wax on the letter. This is simple evidence to show that there is nothing haram about imitating the norms of modern culture. Islamic culture by and large is not necessarily 'Islamic'; meaning we are allowed to be broad-minded in this regard. E.g. etiquette, mannerisms, dialogues, clothes, cuisine, etc. is all open - you follow what society is doing.
7. Notice as well the Prophet PBUH addresses the rulers with their highest titles; and this was also a part of the etiquette.
8. One fiqh point: In the letter to the people of Oman, the Prophet PBUH said, "Take jizya from the Majus." This creates controversy in the 4 madhahib: Two madhhabs have said jizya can only be taken from the People of the Book i.e. Jews and Christians; Whereas Hanafis and most of the later Malikis believe it can be taken from anybody. The evidences show that the second position is the stronger one. Majus are not among the People of the Book, yet the Prophet PBUH said jizya is to be taken from them.
9. Final point: Recall the Prophet PBUH said to Caesar, "If you reject, the sins of the Arisiyun/Arisiyin will be on you." Now, the term 'Arisiyun' is not an Arabic word. So people struggled what did the Prophet PBUH mean by this? In our times, a famous scholar from India, Abul Hasan Ali Hasani Nadwi says, "Arisiyun means the followers of Aris. Aris is the Arabic of Arius. Arius is an 'infamous' Christian theologian who died 336 CE." Arius preached a very different version of Christianity, and it lines up far closer with Islamic notion of Jesus. The Arius's 'heresy' became so widespread that when Constantine embraced Christianity, the first thing that they needed to do was to get rid of Arius's version of Christianity, so he gathered a council in Nicaea. And in Nicaea, in the year 325 CE, they debated for weeks on end and came forth with a creed. The main point of the creed was refuting Arius. And the Arius's 'heresy' was made official that all people who followed him were exiled. And in the creed it's said, "Anyone who has the books of Arius shall be burned and killed." So the writings of Arius are almost nonexistent now. All of the information we have about Arius comes from his enemies, and we don't know for sure what exactly he said, but clearly his teachings are much closer to Islam than any other version of Christianity.
The fact that the Prophet PBUH is writing 2.5 centuries later, referring to Christians as Arisiyun is very profound. (And again, Arisiyun means the followers of Arius. And this seems to be the correct opinion; why? Because to Khosrow the Prophet PBUH said, "If you reject, the sins of the Majus will be on you." And this parallels what he said to Caesar, "If you reject, the sins of the Arisiyun will be on you.") It's as if the Prophet PBUH is saying, "Look. The Arisiyun are the closest to Islam; if you allow them to hear my message, they will embrace. But if you deny my message to them, then the group that will for sure convert, you will be responsible for them on the Day of Judgement." And this of course is amazing simply because no Arab could have known about Arisiyun.
And to give you an idea about how close Islam is to the belief of Arius: Peter the Venerable, who was the abbot of Cluny, and the first person to study Islam academically in order to refute it and translate the Quran into Latin, writes a refutation of Islam, and in it he says, "Muhammad is the successor to Arius." So he sees in our theology echos of Arius's theology. And of course the Islamic position of Isa AS is that he is not divine nor the son of God. Arius, his belief might not have been exactly like that, but no doubt he does not believe in the divinity of Jesus the way that the other Christian groups believe in.
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As a sidenote: None of the physical letters (or the shoes, the ring, the clothes, etc.) of the Prophet PBUH have been preserved. What we may see online is not authentic. It is just not possible for these items to be preserved for 14+ centuries, especially the letters.