Sunan Abi Dawud, Book 3, Hadith 817 (USC-MSA) ⓘ
Abu sa’id said: we were commanded to recite Fatihat al-kitab and whatever was convenient (from the Qur’an during the prayer).
حَدَّثَنَا أَبُو الْوَلِيدِ الطَّيَالِسِيُّ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، عَنْ أَبِي نَضْرَةَ، عَنْ أَبِي سَعِيدٍ، قَالَ أُمِرْنَا أَنْ نَقْرَأَ، بِفَاتِحَةِ الْكِتَابِ وَمَا تَيَسَّرَ .
also referenced under: Hadith 818 (DarusSalam) & Hadith 817 (Hasan)