Sahih al-Bukhari 7392
Sahih al-Bukhari · Book 97: Oneness, Uniqueness of Allah (Tawheed) · Allah has one hundred Names less One
Narrated Abu Huraira:
حَدَّثَنَا أَبُو الْيَمَانِ ، أَخْبَرَنَا شُعَيْبٌ ، حَدَّثَنَا أَبُو الزِّنَادِ ، عَنِ الأَعْرَجِ ، عَنْ أَبِي هُرَيْرَةَ ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِنَّ لِلَّهِ تِسْعَةً وَتِسْعِينَ اسْمًا مِائَةً إِلاَّ وَاحِدًا، مَنْ أَحْصَاهَا دَخَلَ الْجَنَّةَ " . {أَحْصَيْنَاهُ} حَفِظْنَاهُ .
Allah's Messenger (ﷺ) said, "Allah has ninety-nine Names, one-hundred less one; and he who memorized them all by heart will enter Paradise." To count something means to know it by heart.