Musannaf Ibn Abi Shayba 21:403

Abu al-Ahwas narrated to us, from Abu Ishaq, from al-Aswad and Alqama, who said: Abdullah said: "Indeed, there are two verses in the Book of Allah; no servant commits a sin, then recites them and seeks forgiveness from Allah, except that He forgives him: 'And those who, when they commit an immorality or wrong themselves [by transgression], remember Allah and seek forgiveness for their sins - and who can forgive sins except Allah?' (3:135) to the end of the verse. And: 'And whoever does a wrong or wrongs himself but then seeks forgiveness of Allah will find Allah Forgiving and Merciful.' (4:110)"