I asked the Messenger of Allah (s): Who is your deputy from your Nation, for no prophet is raised except that he has a deputy from his Nation? So, the Messenger of Allah (s) said: It has yet to be revealed to me. So, I remained for as long as Allah willed for me to remain; then I entered the mosque, and the Messenger of Allah (s) called me and said: O Salman! You asked me about the deputy of my Nation – do you know who the deputy of Musa from his Nation was? So, I said: His deputy was a young man, Yusha` b. Nun. He said: Do you know why he was appointed? I said: Allah and His Messenger know best. He said: He deputed him because he was the most knowledge person in his Nation after him. My deputy is the most knowledgeable person from my Nation after me – `Ali b. Abi Talib.