Ali to the Prophet as Aaron was to Moses:
"Narrated Sad: Allah's Apostle set out for Tabuk. appointing 'Ali as his deputy (in Medina). 'Ali said, 'Do you want to leave me with the children and women?' The Prophet said, 'Will you not be pleased that you will be to me like Aaron to Moses? But there will be no prophet after me.' (Translation of Sahih Bukhari, Book 59, Military Expeditions led by the Prophet (peace be upon him) (Al-Maghaazi), Volume 5, Number 700)"
"Narrated Ubaida: Ali said (to the people of 'Iraq), "Judge as you used to judge, for I hate differences (and I do my best ) till the people unite as one group, or I die as my companions have died." And narrated Sad that the Prophet said to 'Ali, 'Will you not be pleased from this that you are to me like Aaron was to Moses?' (Translation of Sahih Bukhari, Book 57, Companions of the Prophet, Volume 5, Number 56)"
"Sa'd b. Abi Waqqas reported that Allah's Messenger (may peace be upon him) left 'Ali b. Abi Talib behind him (as he proceeded) to the expedition of Tabuk, whereupon he ('Ali) said: Allah's Messenger, are you leaving me behind amongst women 4nd children? Thereupon he (the Holy Prophet) said: Aren't you satisfied with being unto me what Aaron was unto Moses but with this exception that there would be no prophet after me. (Translation of Sahih Muslim, Book 31, The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fada'il Al-Sahabah), Number 5914)"
"Sa'd reported Allah's Apostle (may peace be upon him) as saying to 'Ali: Aren't you satisfied with being unto me what Aaron was unto Moses? (Translation of Sahih Muslim, Book 31, The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fada'il Al-Sahabah), Number 5916)"