Musnad Ahmad 33:523

Shadhan Aswad ibn Amir narrated to us, Sharik narrated to us, from Abdullah ibn Muhammad ibn Aqil, from Jabir ibn Abdullah, who said: When the Messenger of Allah, peace and blessings of Allah be upon him, wanted to leave Ali behind, Ali said to him: "What will the people say about me if you leave me behind?" He said: He replied to him: "Are you not pleased that you are to me in the position of Aaron to Moses? Except that there is no prophet after me," or "There shall be no prophet after me."