Musannaf Ibn Abi Shayba 33:297

Abu Mu'awiyah narrated to us, from al-A'mash, from Ibrahim al-Taymi, from al-Harith ibn Suwayd, who said: Abdullah said: "I would have wished that a piece of dung had slipped away from me, and I was attributed to it, and was called 'Abdullah ibn Rawthah' (Abdullah son of Dung), and that Allah had forgiven me one sin." Except that Abu Mu'awiyah said: "I would have wished that I knew that Allah had forgiven me," then he mentioned the like of it.