Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 416
'A'isha reported: I said: Messenger of Allah, the son of Jud'an established ties of relationship, fed the poor. Would that be of any avail to him? He said: It would be of no avail to him as he did not ever say: O my Lord, pardon my sins on the Day of Resurrection.