Sahih Muslim Book 37, Hadith Number 6642.

Abu Huraira reported from Allah’s Messenger (may peace be upon him) that his Lord, the Exalted and Glorious, thus said. A servant committed a sin and he said: O Allah, forgive me my sins, and Allah (the Exalted and Glorious)said:My servant committed a sin and then he came to realise that he has a Lord Who forgives the sins and takes to account (the sinner) for the sin. He then again committed a sin and said: My Lord, forgive me my sin, and Allah, the Exalted and High, said: My servant committed a sin and then came to realise that he has a Lord Who would forgive his sin or would take (him) to account for the sin. He again committed a sin and said: My Lord, forgive me for my sin, and Allah (the Exalted and High) said: My servant has committed a sin and then came to realise that he has a Lord Who forgives the sins or takes (him) to account for sin. O servant, do what you like. I have granted you forgiveness.

‘Abd al-A’la said: I do not know whether he said thrice or four times to do “what you desire”. The hadith has been narrated on the authority of ‘Abd al-A’la b. Hammad with the same chain of transmitters.