Musnad Ahmad 5:320

Aswad ibn Amir narrated to us, Sharik narrated to us, from al-A'mash, from al-Minhal, from Abbad ibn Abdullah al-Asadi, from Ali, who said: When this verse was revealed: "And warn your closest kindred" [Ash-Shu'ara: 214], the Prophet, peace and blessings of Allah be upon him, gathered his household, and thirty [people] gathered. They ate and drank. He said: He said to them, "Who will guarantee my debt and my promises for me, and be with me in Paradise, and be my successor among my family?" A man—whom Sharik did not name—said: O Messenger of Allah, you are like an ocean; who can undertake this? He said: Then he said it to another. He said: So he presented that to his household, and Ali said: "I will."