Sahih Muslim
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-Fadail Al-Sahabah)
Book Number: 031 / Hadith Number: 5916
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?