Hadithcore
Sunan Abi Dawud, 818
sahih· Al-Albani

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 ‏.‏

References2 variants
In-Book Reference
Book 2, Hadith 428
English Reference
Book 2, Hadith 817