Musnad Ahmad 30:2386

Isma'il narrated to us, from Hisham, and Yazid—meaning Ibn Harun—said: Hisham informed us, from Ibn Sirin, from Abu Hurayrah, who said: The Messenger of Allah, may Allah bless him and grant him peace, said: "To Allah, the Almighty and Majestic, belong ninety-nine names, one hundred minus one. Whoever enumerates them all will enter Paradise."