Sunan Abi Dawud, Hadith 787 ⓘ
Ibn Abbas said: The prophet did not distinguish between the two surahs until the words “In the name of Allah, the Compassionate, the merciful” was revealed to him. These are the words of Ibn al-sarh.
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، وَأَحْمَدُ بْنُ مُحَمَّدٍ الْمَرْوَزِيُّ، وَابْنُ السَّرْحِ، قَالُوا حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرٍو، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، - قَالَ قُتَيْبَةُ فِيهِ - عَنِ ابْنِ عَبَّاسٍ، قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم لاَ يَعْرِفُ فَصْلَ السُّورَةِ حَتَّى تُنَزَّلَ عَلَيْهِ { بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ } . وَهَذَا لَفْظُ ابْنِ السَّرْحِ .
also referenced under: Hadith 788 (DarusSalam) & Book 3, Hadith 787 (USC-MSA)