Abu Abdullah al-Jadali said: I heard Sa'd (may Allah be pleased with him) say: The Messenger of Allah (peace and blessings be upon him) said to Ali: "You are to me in the position that Harun (peace be upon him) had to Musa (peace be upon him), except that there is no prophet after me."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 331