The Prophet wrote to the Caesar of the Byzantine Empire, inviting him to Islam, sending a letter to him with Dihya al-Kalbi. The Prophet directed him to present the letter to the governor of Busra, who would forward it to Caesar.
When God had relieved him of the Persian armies, Caesar walked from Emesa [in central Syria] to Jerusalem, out of gratitude to God for having inured him to trial. So when the letter of the Prophet reached him, Caesar read it and said, "Look for someone from his people around here, so that I may ask about this Messenger of God."
Now, it happened that Abu Sufyan was then in Syria with some men from the Quraish tribe who had come on business during the truce that then existed between the Prophet and the disbelievers of the Quraish.
Abu Sufyan later said, "The emissary of Caesar found us in a part of Syria, and he took me and my companions to Jerusalem. There we were brought to Caesar, who was sitting at his royal court, his crown on his head, around him the grandees of Byzantium."
Now, Caesar said to his interpreter, "Ask them who among them is closest in kinship to this man who claims to be a prophet."
Abu Sufyan [who was not a Muslim at the time] responded that he was nearest of them in kinship.
Caesar asked, "And what is the relationship between you and him?"
Abu Sufyan said, "He is a son of my paternal uncle." Then Caesar said, "Bring him closer," and had Abu Sufyan's companions placed behind him, at his shoulders. Then he told his interpreter, "Tell his companions that I am going to question him about this man who claims to be a prophet; so if he tells a lie, immediately repudiate it as a lie."
Later Abu Sufyan admitted that he would have lied when asked about the Prophet, if not for the fact that he would have been shamed to have others spreading reports that he was a liar. So he told the truth.
Now, Caesar asked through his interpreter, "How is the lineage of this man among you?"
Abu Sufyan replied, "He is of noble descent among us." Caesar asked, "And has any one of your people previously said what he has said?"
