Musnad Abu Ya'la al-Mawsili 1:13

Ubayd Allah ibn Umar al-Qawariri narrated to us, Ghundar narrated to us, Shu'bah narrated to us, he said: I heard Uthman ibn al-Mughirah al-Thaqafi, he said: I heard Ali ibn Rabi'ah from a man from Banu Fazarah who is called Asma, from Ali ibn Abi Talib, he said: "When I heard something from the Messenger of Allah (may Allah bless him and grant him peace), Allah would benefit me with it as much as He willed to benefit me. Abu Bakr narrated to me—and Abu Bakr spoke the truth—from the Prophet (may Allah bless him and grant him peace) that he said: 'There is no servant'—Shu'bah said: I think he said 'a Muslim'—'who commits a sin, then performs ablution, then prays two rak'ahs, then seeks Allah's forgiveness for that sin, except that He forgives him.' Shu'bah said: And he recited one of these two verses: 'Whoever does evil will be recompensed for it' (An-Nisa: 123), and 'And those who, when they commit an immorality or wrong themselves...' (Al-Imran: 135)."