Sahih Muslim Book 37, Hadith Number 6622.
Chapter : The obliteration of sins with the help of seeking forgiveness from Allah.
Abu Huraira reported Allah’s Messenger (may peace be upon him) having said: By Him in Whose Hand is my life, if you were not to commit sin, Allah would sweep you out of existence and He would replace (you by) those people who would commit sin and seek forgiveness from Allah, and He would have pardoned them.