ENOfficial
Abu Huraira told that he heard God's messenger say God most high had inscribed a document before bringing the creation into being, "My mercy has preceded my anger," and that it is written in His presence above the throne. (Bukhari and Muslim.)
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَبِي هُرَيْرَةَ قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: " إِنَّ اللَّهَ تَعَالَى كَتَبَ كِتَابًا قَبْلَ أَنْ يَخْلُقَ الْخَلْقَ: إِنَّ رَحْمَتِي سَبَقَتْ غَضَبِي فَهُوَ مَكْتُوب عِنْده فَوق الْعَرْش ". مُتَّفق عَلَيْهِ
sunnah.com