Kitab al-Kafi
In Kitab al-Kafi, Imam Hasan al-Askari narrates that the greatest name of Allah has seventy three letters and Asif only knew one. With that letter, the land between him and the throne of the Queen of Sheeba shrunk such that he was able to place the throne before Sulayman and the land returned to its original state before the blinking of an eye. He then further states that the Imams of Ahl al-Bayt know seventy two of the letters and the final letter is kept exclusively with Allah as knowledge of the ghaib.