Musannaf Ibn Abi Shayba 3:5265

Waki’ narrated to us, [he said] Mis’ar narrated to us, from Uthman ibn al-Mughirah al-Thaqafi, from Ali ibn Rabi’ah al-Walibi, from Asma ibn al-Hakam al-Fazari, from Ali, who said: "When I heard a hadith from the Messenger of Allah (may Allah bless him and grant him peace), Allah would benefit me with it as much as He willed. But when someone else narrated it to me from him, I would ask him to swear an oath, and if he swore to me, I would believe him. Abu Bakr narrated to me—and Abu Bakr spoke the truth—that he said: The Messenger of Allah (may Allah bless him and grant him peace) said: 'There is no man who commits a sin, then performs ablution and perfects the ablution, then prays'—Sufyan said: 'Then prays two rak'ahs'—Mis’ar said: 'Then prays and seeks the forgiveness of Allah, except that He forgives him.'"