Al-Bukhari gave a long narration of the contents of the letter sent by the Prophet (Peace be upon him) 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 (Peace be upon him)]: ‘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.’ ” [3:64]

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 (Peace be upon him) 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 (Peace be upon
him). 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 man 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 . 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 (Peace be upon him)] 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
(Peace be upon him) 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.