Abu Dawud Book 36, Hadith Number 5145.
Chapter : Not known.
Narated By Abdullah ibn Umar : A man came to the Prophet (PBUH) and asked: Apostle of Allah! how often shall I forgive a servant? He gave no reply, so the man repeated what he had said, but he still kept silence. When he asked a third time, he replied: Forgive him seventy times daily.