Hadith 4553 of the book of commentary by sahih al bukhari

Narrated Ibn `Abbas: Abu Sufyan narrated to me personally, saying, I set out during the Truce that had been concluded between me and Allah's Messenger . While I was in Sham, a letter sent by the Prophet was brought to Heraclius. Dihya Al-Kalbi had brought and given it to the governor of Busra, and the latter forwarded it to Heraclius. Heraclius said, 'Is there anyone from the people of this man who claims to be a prophet?' The people replied, 'Yes.' So I along with some of Quraishi men were called and we entered upon Heraclius, and we were seated in front of him. Then he said, 'Who amongst you is the nearest relative to the man who claims to be a prophet?' So they made me sit in front of him and made my companions sit behind me. Then he called upon his translator and said (to him). 'Tell them ( i.e. Abu Sufyan's companions) that I am going to ask him (i.e. Abu Sufyan) regarding that man who claims to be a prophet. So, if he tell me a lie, they should contradict him (instantly).' By Allah, had I not been afraid that my companions would consider me a liar, I would have told lies. Heraclius then said to his translator, 'Ask him: What is his (i.e. the Prophet's) family status amongst you? I said, 'He belongs to a noble family amongst us. Heraclius said, 'Was any of his ancestors a king?' I said, 'No.' He said, 'Did you ever accuse him of telling lies before his saying what he has said?' I said, 'No.' He said, 'Do the nobles follow him or the poor people?' I said, 'It is the poor who followed him.' He said, 'Is the number of his follower increasing or decreasing?' I said, 'The are increasing.' He said, 'Does anyone renounce his religion (i.e. Islam) after embracing it, being displeased with it?' I said, 'No.' He said, 'Did you fight with him?' I replied, 'Yes.' He said, 'How was your fighting with him?' I said, 'The fighting between us was undecided and victory was shared by him and us by turns. He inflicts casualties upon us and we inflict casualties upon him.' He said, 'Did he ever betray?' I said, 'No, but now we are away from him in this truce and we do not know what he will do in it Abu Sufyan added, By Allah, I was not able to insert in my speech a word (against him) except that. Heraclius said, 'Did anybody else (amongst you) ever claimed the same (i.e. Islam) before him? I said, 'No.' Then Heraclius told his translator to tell me (i.e. Abu Sufyan), 'I asked you about his family status amongst you, and you told me that he comes from a noble family amongst you Verily, all Apostles come from the noblest family among their people. Then I asked you whether any of his ancestors was a king, and you denied that. Thereupon I thought that had one of his fore-fathers been a king, I would have said that he (i.e. Muhammad) was seeking to rule the kingdom of his fore-fathers. Then I asked you regarding his followers, whether they were the noble or the poor among the people, and you said that they were only the poor (who follow him). In fact, such are the followers of the Apostles. Then I asked you whether you have ever accused him of telling lies before saying what he said, and your reply was in the negative. Therefore, I took for granted that a man who did not tell a lie about others, could ever tell a lie about Allah. Then I asked you whether anyone of his followers had renounced his religion (i.e. Islam) after embracing it, being displeased with it, and you denied that. And such is Faith when it mixes with the cheerfulness of the hearts. Then I asked you whether his followers were increasing or decreasing. You claimed that they were increasing. That is the way of true faith till it is complete. Then I asked you whether you had ever fought with him, and you claimed that you had fought with him and the battle between you and him was undecided and the victory was shared by you and him in turns; he inflicted casual ties upon you and you inflicted casualties upon them. Such is the case with the Apostles; they are out to test and the final victory is for them. Then I asked you whether he had ever betrayed; you claimed that he had never betrayed. I need, Apostles never betray. Then I asked you whether anyone had said this statement before him; and you denied that. Thereupon I thought if somebody had said that statement before him, then I would have said that he was but a man copying some sayings said before him. Abu Safyan said, Heraclius then asked me, 'What does he order you to do?' I said, 'He orders us (to offer) prayers and (to pay) Zakat and to keep good relationship with the Kith and kin and to be chaste.' Then Heraclius said, 'If whatever you have said, is true, he is really a prophet, and I knew that he ( i.e. the Prophet ) was going to appear, but I never thought that he would be from amongst you. If I were certain that I can reach him, I would like to meet him and if I were with him, I would wash his feet; and his kingdom will expand (surely to what is under my feet.' Then Heraclius asked for the letter of Allah's Messenger and read it wherein was written: In the Name of Allah, the Most Beneficent, the Most Merciful. This letter is) from Muhammad, Apostle of Allah, to Heraclius, the sovereign of Byzantine........ Peace be upon him who follows the Right Path. Now then, I call you to embrace Islam. Embrace Islam and you will be saved (from Allah's Punishment); embrace Islam, and Allah will give you a double reward, but if you reject this, you will be responsible for the sins of all the people of your kingdom (Allah's Statement):-- O the people of the Scripture (Jews and Christians)! Come to a word common to you and us that we worship None but Allah....bear witness that we are Muslims.' (3.64) When he finished reading the letter, voices grew louder near him and there was a great hue and cry, and we were ordered to go out. Abu Sufyan added, While coming out, I said to my companions, 'The situation of Ibn Abu Kabsha (i.e. Muhammad) has become strong; even the king of Banu Al14 Asfar is afraid of him.' So I continued to believe that Allah's Messenger would be victorious, till Allah made me embrace Islam. Az-Zuhri said, Heraclius then invited all the chiefs of the Byzantines and had them assembled in his house and said, 'O group of Byzantines! Do you wish to have a permanent success and guidance and that your kingdom should remain with you?' (Immediately after hearing that), they rushed towards the gate like onagers, but they found them closed. Heraclius then said, 'Bring them back to me.' So he called them and said, 'I just wanted to test the strength of your adherence to your religion. Now I have observed of you that which I like.' Then the people fell in prostration before him and became pleased with him. (See Hadith No. 6,Vol 1)