Musnad Ahmad 30:3249

Bahz narrated to us, he said: Hammad narrated to us, he said: Ishaq ibn Abdullah ibn Abi Talhah narrated to us, from Abd al-Rahman ibn Abi Amrah, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said, narrating from his Lord, the Almighty and Majestic: "My servant committed a sin, so he said: 'O Lord, forgive me my sin.' So He (the Almighty and Majestic) said: 'My servant committed a sin, and he knew that he has a Lord who forgives the sin and takes to account for the sin'—three times. Then He says: 'Do what you wish, for I have forgiven you.'"