The Messenger of Allah ﷺ said, "When Allah completed the creation, He wrote in His book, which is with Him above the Throne, 'My mercy has prevailed over My wrath.'"
قال رسول الله ﷺ: لما قضى الله الخلق كتب في كتابه فهو عنده فوق العرش إن رحمتي غلبت غضبي.
Bukhari narrated it in the Beginning of Creation (3194), and Muslim in Repentance (2751), both from Qutayba bin Saeed, who said, Mughira bin Abdul-Rahman Qurashi narrated to us, from Abu Zinad, from Araj, from Abu Hurairah, who mentioned it.