Musnad Ahmad 5:214

Abu Sa’id, the freed slave of Banu Hashim, narrated to us, Yahya ibn Salamah—meaning Ibn Kuhayl—narrated to us, he said: I heard my father narrating from Habbah al-‘Arani, who said: I saw ‘Ali laugh upon the pulpit; I have never seen him laugh a laugh more than that, until his molars appeared. Then he said: I remembered the statement of Abu Talib. Abu Talib appeared to us while I was with the Messenger of Allah (peace and blessings of Allah be upon him), and we were praying in the valley of Nakhlah. He said: "What are you two doing, O son of my brother?" The Messenger of Allah (peace and blessings of Allah be upon him) invited him to Islam. He said: "There is no harm in what you are doing, or no harm in what you are saying, but by Allah, my posterior shall never be raised above me." And he laughed in amazement at the statement of his father. Then he said: "O Allah, I do not acknowledge that any servant of Yours from this nation worshipped You before me, except for Your Prophet"—three times—"I have prayed seven years before the people prayed."