Heraclius summoned his interpreter, then called for the letter of the Prophet ﷺ and had it read out, "In the name of Allah, the Most Merciful, the Most Compassionate. From Muhammad, the servant of Allah and His Messenger, to Heraclius," and "People of the Book, come to a word common between us and you" [Al Imran 3:64], to the end of the verse.
وقال ابن عباس أخبرني
أن هرقل، دعا ترجمانه، ثم دعا بكتاب النبي ﷺ فقرأه بسم الله الرحمن الرحيم من محمد عبد الله ورسوله إلى هرقل، و{يا أهل الكتاب تعالوا إلى كلمة سواء بيننا وبينكم} الآية.