Sunan Ibn Majah, Hadith 189 ⓘ
It was narrated that Abu Hurairah said: "The Messenger of Allah said: 'Your Lord wrote for Himself with His Own Hand before He created the creation: "My mercy precedes My wrath."
حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى، حَدَّثَنَا صَفْوَانُ بْنُ عِيسَى، عَنِ ابْنِ عَجْلاَنَ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " كَتَبَ رَبُّكُمْ عَلَى نَفْسِهِ بِيَدِهِ قَبْلَ أَنْ يَخْلُقَ الْخَلْقَ رَحْمَتِي سَبَقَتْ غَضَبِي " .
also referenced under: Book 1, Hadith 194 (In-Book) & Volume 1, Book 1, Hadith 189 (DarusSalam)