(12) باب إِنَّ لِلَّهِ مِائَةَ اسْمٍ إِلاَّ وَاحِدًا
Narrated Abu Huraira:
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.
Reference: Sahih al-Bukhari 7392
In-book reference: Book 97, Hadith 21
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 9, Book 93, Hadith 489