Sahih Muslim
The Book Pertaining to Repentance and Exhortation to Repentance (Kitab Al-Tauba)
Book Number: 037 / Hadith Number: 6626
Abu Huraira reported that Allah's Messenger (may peace be upon him) said: When Allah created the creation as He was upon the Throne, He put down in His Book: Verily, My mercy predominates My wrath.