Usul al-Kafi
Book 4:
The Book of Divine Proof

Chapter 36
What was bestowed on the Imams from the greatest (sublime) name of God

373. 2. Imam Jafar as-Sadiq (p): Prophet Isa (Jesus) (p) was given two letters (of the divine alphabet) by God, and with them he performed miracles. Prophet Musa (Moses) (p) was given four letters, Prophet Ibrahim (Abraham) (p) was given eight letters, Prophet Nuh (Noah) (p) was given fifteen letters, Prophet Adam (p) twenty five letters, and God gave the total of all of them to Prophet Muhammad (p). The Greatest Name of God possesses seventy three letters and the Prophet Muhammad (p) was presented seventy two letters and one letter remained veiled even from him.

374. 3. Imam Ali an-Naqi (p): The Greatest Name of God has seventy-three letters. Asif (p) (the cousin and minister of Prophet Sulayman (Solomon) (p)) possessed one letter, and when he spoke with it, the earth between him and Saba (Sheba) folded up for him, and he took the throne of Bilqis, and brought it to Prophet Sulayman (Solomon) (p), and the ground opened up in time less than the twinkling of an eye. With us are seventy two of the letters, and one letter is with God, which is kept exclusively in (His) Knowledge of the unknown.