Musnad Abu Ya'la al-Mawsili 117:159

Amr ibn al-Dahhak narrated to us, my father narrated to us, Mustawrid Abu Hammam narrated to us, Thabit narrated to us, from Anas, who said: A man came to the Prophet, may Allah bless him and grant him peace, and said: "O Messenger of Allah, I have not left a *hajah* (a minor sin) nor a *dajah* (a major sin) except that I have committed it." He said: "Do you not testify that there is no god but Allah and that Muhammad is the Messenger of Allah?" [He said it] three times. He said: "Yes." He said: "That wipes away that."