Abu Sufyan told me this directly, mouth to mouth. He said, "I set out during the period of truce between me and the Messenger of Allah ﷺ. While I was in Syria, a letter arrived from the Prophet ﷺ addressed to Heraclius, and it was Dihya Kalbi who had brought it." He then related the story in full detail.The letter of the Messenger of Allah ﷺ read, "In the name of Allah, the Most Compassionate, the Most Merciful. From Muhammad, the Messenger of Allah, to Heraclius, the great one of the Byzantines. Peace be upon whoever follows guidance. I call you with the call of Islam. Accept Islam and you will be safe. Accept Islam and Allah will grant you your reward twice over. But if you turn away, then upon you rests the sin of your subjects. 'People of the Book, come to a word that is equitable between us and you, that we worship none but Allah' up to His words, 'bear witness that we are Muslims'" [Al Imran 3:64].
حدثني أبو سفيان من فيه إلى في قال: انطلقت في المدة التي كانت بيني وبين رسول الله ﷺ، قال: فبينا أنا بالشام إذ جيء بكتاب من النبي ﷺ إلى هرقل، وكان دحية الكلبي جاء به… فذكر القصة بالتفصيل، وجاء في كتاب رسول الله ﷺ: بسم الله الرحمن الرحيم، من محمد رسول الله إلى هرقل عظيم الروم، سلام على من اتبع الهدى، أما بعد: فإني أدعوك بدعاية الإسلام، أسلم تسلم، وأسلم يؤتك الله أجرك مرتين، فإن توليت فإن عليك إثم الأريسين، {و يا أهل الكتب تعالوا إلى كلمة سواء بيننا وبينكم ألا نعبد إلا الله} إلى قوله: {أشهدوا بأنا مسلمون}.
Bukhari narrated it in the Tafsir (4553) and Muslim in the Jihad and Expeditions (1773), both from the hadith of Abdul-Razzaq, who said, Mamar informed us, from Zuhri, who said, Ubaydullah bin Abdullah bin Utba informed me, who said, Ibn Abbas narrated to me, who said, and he mentioned it.In this hadith is evidence that Surah Al Imran was revealed after Hudaybiya and before the Conquest, and more specifically his saying, the Exalted, "Say, O People of the Scripture, come to a word common between us and you, that we worship none but Allah, and that we associate nothing with Him, and that none of us take others as lords besides Allah. But if they turn away, then say, 'Bear witness that we are Muslims.'" [Al Imran 3:64], and that the Prophet ﷺ also recited it to the delegation of Najran who came to the Messenger of Allah ﷺ after the Conquest.In this is also a rebuttal of the statement of Muhammad bin Ishaq and others that the opening of Surah Al Imran, up to some eighty-odd verses of it, was revealed concerning the delegation of Najran. And even if his statement is correct, then the noble verse that the Messenger of Allah ﷺ wrote to Heraclius was certainly revealed before the delegation of Najran.