al-bukhari gave a long narration of the contents of the letter sent by the prophet [pbuh] to hercules, king of the byzantines:
"in the name of allâh, the most beneficent, the most merciful.
from muhammad, the slave of allâh and his messenger to hercules, king of the byzantines.
blessed are those who follow true guidance. i invite you to embrace islam so that you may live in security. if you come within the fold of islam, allâh will give you double reward, but in case you turn your back upon it, then the burden of the sins of all your people shall fall on your shoulders.
"say (o muhammad [pbuh]): ‘o people of the scripture (jews and christians), come to a word that is just between us and you, that we worship none but allâh, and that we associate no partners with him, and that none of us shall take others as lords besides allâh.’ then, if they turn away, say: ‘bear witness that we are muslims.’ " [al-qur'an 3:64][sahih al-bukhari 1/4,5]
the muslim envoy, dihyah bin khalifah al-kalbi, was ordered to hand the letter over to king of busra, who would in turn, send it to caesar.
incidentally, abu sufyan bin harb, who by that time had not embraced islam, was summoned to the court and hercules asked him many questions about muhammad [pbuh] and the religion which he preached. the testimony which this avowed enemy of the prophet gave regarding the personal excellence of the prophet’s character and the good that islam was doing the human race, left hercules wonder-struck.
al-bukhâri, on the authority of ibn abbas, narrated that hercules sent for abu sufyan and his companions, who happened to be trading in ash-sham, jerusalem. that was during the truce that had been concluded between the polytheists of quraish and the messenger of allâh [pbuh]. hercules, seated amongst his chiefs of staff, asked, "who amongst you is the nearest relative to the man who claims to be a prophet?" "i (abu sufyan) replied: ‘i am the nearest relative to him from amongst the group.’ 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 men who claims to be a prophet. so if he tells a lie, they should contradict him (instantly)’. by allâh had i not been afraid that my companions would consider me a liar, i would have told lies", abu sufyan later said.
abu sufyan’s testimony went as follows: "muhammad descends from a noble family. no one of his family happened to assume kingship. his followers are those deemed weak with numbers ever growing. he neither tells lies nor betrays others, we fight him and he fights us but with alternate victory. he bids people to worship allâh alone with no associate, and abandon our fathers’ beliefs. he orders us to observe prayer, honesty, abstinence and maintain strong family ties." "hercules, on hearing this testimony, turned to his translator bidding him to communicate to us his following impression which reveals full conviction in the truthfulness of muhammad’s prophethood: ‘i fully realize that prophets come from noble families; he does not affect any previous example of prophethood. since none of his ancestors was a monarch, we cannot then allege that he is a man trying to reclaim his father’s monarchy. so long as he does not tell lies to people, he is for the more reason, immune to telling lies as regards allâh. concerning his followers being those deemed weak with numbers ever growing, it is something that goes in agreement with questions of faith until this latter assumes its full dimensions geographically and demographically. i have understood that no instance of apostasy has as yet appeared among his followers, and this points to the bliss of faith that finds its abode in the human heart. betrayal, as i see, is alien to him because real prophets hold betrayal in abhorrence. bidding worship of allâh with no associates, observance of prayer, honesty and abstinence and prohibition of paganism are traits bound to subject to him all my possessions. i have already known that a prophet must arise but it has never occurred to me that he will be an arab from among you. if i was sure i would be faithful to him, i might hope to meet him, and if i were with him, i would wash his feet.’ hercules then requested that the prophet’s letter be read. the observations of the emperor and finally the definite and clear-cut exposition of the islamic message could not but create a tense atmosphere amongst the clergy present at the court. we were ordered to go out." abu sufyan said, "while coming out, i said to my companions, ‘the matter of ibn abi kabshah (i.e. muhammad [pbuh]) has become so prominent that even the king of banu al-asfar (i.e. the romans) is afraid of him.’ so i continued to believe that allâh’s messenger [pbuh] would be victorious, till allâh made me embrace islam." the king did not embrace islam — for it was differently ordained. however, the muslim envoy was returned to madinah with the felicitations of the emperor.
on his way back to madinah, dihyah al-kalbi was intercepted by people from judham tribe in hasmi, who looted the presents sent to the prophet [pbuh]. zaid bin haritha at the head of five hundred men was despatched to that spot, inflicted heavy losses on those people and captured 1000 camels, 5000 of their cattle and a hundred women and boys. the chief of judham who had embraced islam filed a complaint with the prophet, who gave a positive response to the former’s protest, and ordered that all the spoils and captives be returned.