Sahih Bukhari
Oneness, Uniqueness of Allah (Tawheed)
Volume: 009 / Book Number: 093 / Hadith Number: 501
Narrated Abu Huraira:
The Prophet said, "When Allah created the Creation, He wrote in His Book--and He wrote (that) about Himself, and it is placed with Him on the Throne--'Verily My Mercy overcomes My Anger.'"