It is narrated from Sayyidah Asma' bint Umays (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) said to Ali (may Allah be pleased with him): "You are to me in the position that Harun (peace be upon him) had with Musa (peace be upon him), except that there is no prophet after me."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20759