Testimony of Abu Sufyan
The dialogue between the Byzantine Emperor Hirrclius and Abu Sufyan took place after the treaty of Hudaibiyyah. Abu Sufyan has related: When the Emperor summoned me to his presence, he placed my companions behind me and told them that he was about to question me concerning the person who claimed to be a prophet in our country , and that if in my answers I said anything which was not true, they should immediately contradict me. Therefore, had I not been afraid that if I said anything that was untrue my companions would contradict me and I would be humiliated before the Emperor, I would have had recourse to falsehood in my replies. I tried hard to add something to my replies that might go against the Holy Prophet, peace be on him, but I found no opportunity of doing so, except in one respect, and that was when the Emperor asked me: How does he carry out his covenants? I replied: So far, he has not contravened any of his covenants with us. We have just entered into a new treaty with him and we shall see how he behaves in respect of it, whether he carries it out or not. This was all that I was able to introduce into my replies that could raise a doubt with regard to the truth of the Holy Prophet, peace be on him.
One of the questions that the Emperor had put to Abu Sufyan was: Has any of those who have accepted him, repudiated him? To which Abu Sufyan replied in the negative. Had Islam imposed the penalty of death upon an apostate, Abu Sufyan would certainly have taken advantage of it and told the Emperor that none of the followers of the Holy Prophet resiled from his faith because if he did so, he would be put to death. This also is strong evidence that Islam had not imposed any penalty for apostacy.