Narrated Ibn 'Abbas:

that Abu Sufyan bin Harb informed him that Hiraql had sent for him while he was with a party of the Quraish, and they were trading in Ash-Sham, so they went to him." And he mentioned the Hadith and said: "Then he called for the letter of the Messenger of Allah ﷺ to be read, and it said in it: 'In the Name of Allah, the Merciful, the Beneficent. From Muhammad, Allah's Slave and His Messenger, to Hiraql the leader of Rome. Peace be upon whoever follows the guidance. To proceed:"

حَدَّثَنَا سُوَيْدُ بْنُ نَصْرٍ، أَنْبَأَنَا عَبْدُ اللَّهِ بْنُ الْمُبَارَكِ، أَنْبَأَنَا يُونُسُ، عَنِ الزُّهْرِيِّ، أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّهُ أَخْبَرَهُ أَنَّ أَبَا سُفْيَانَ بْنَ حَرْبٍ أَخْبَرَهُ أَنَّ هِرَقْلَ أَرْسَلَ إِلَيْهِ فِي نَفَرٍ مِنْ قُرَيْشٍ وَكَانُوا تُجَّارًا بِالشَّامِ فَأَتَوْهُ فَذَكَرَ الْحَدِيثَ قَالَ ثُمَّ دَعَا بِكِتَابِ رَسُولِ اللَّهِ ﷺ فَقُرِئَ فَإِذَا فِيهِ بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ مِنْ مُحَمَّدٍ عَبْدِ اللَّهِ وَرَسُولِهِ إِلَى هِرَقْلَ عَظِيمِ الرُّومِ السَّلاَمُ عَلَى مَنِ اتَّبَعَ الْهُدَى أَمَّا بَعْدُ .

قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ وَأَبُو سُفْيَانَ اسْمُهُ صَخْرُ بْنُ حَرْبٍ .