Musannaf Ibn Abi Shayba 33:788

Abu Mu'awiyah narrated to us, from al-A'mash, from Abu Rashid, from 'Ubayd ibn 'Umayr: "For He is ever Forgiving to the oft-returning to Him (al-awwabin)." The "awwab" is the one who remembers his sins in private, then seeks forgiveness for them.