Hadith 43:364
Narrated Abdullah ibn Abbas:
The Prophet (ﷺ) wrote a letter to Heraclius: "From Muhammad, the Messenger of Allah, to Hiraql (Heraclius), Chief of the Byzantines. Peace be to those who follow the guidance." Ibn Yahya reported on the authority of Ibn Abbas that AbuSufyan said to him: We then came to see Hiraql (Heraclius) who seated us before him. He then called for the letter from the Messenger of Allah (ﷺ). Its contents were: "In the name of Allah, the Compassionate, the Merciful, from Muhammad the Messenger of Allah, to Hiraql, chief of Byzantines. Peace be to those who follow the guidance. To proceed."
حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ، وَمُحَمَّدُ بْنُ يَحْيَى، قَالاَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ، عَنْ مَعْمَرٍ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَتَبَ إِلَى هِرَقْلَ " مِنْ مُحَمَّدٍ رَسُولِ اللَّهِ إِلَى هِرَقْلَ عَظِيمِ الرُّومِ سَلاَمٌ عَلَى مَنِ اتَّبَعَ الْهُدَى " . قَالَ ابْنُ يَحْيَى عَنِ ابْنِ عَبَّاسٍ أَنَّ أَبَا سُفْيَانَ أَخْبَرَهُ قَالَ فَدَخَلْنَا عَلَى هِرَقْلَ فَأَجْلَسَنَا بَيْنَ يَدَيْهِ ثُمَّ دَعَا بِكِتَابِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَإِذَا فِيهِ " بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ مِنْ مُحَمَّدٍ رَسُولِ اللَّهِ إِلَى هِرَقْلَ عَظِيمِ الرُّومِ سَلاَمٌ عَلَى مَنِ اتَّبَعَ الْهُدَى أَمَّا بَعْدُ "
Original Reference: Sunan Abi Dawud 5136