Musnad Abu Ya'la al-Mawsili 3:194

Shayban ibn Farrukh narrated to us, Abu al-Rabi' al-Samman narrated to us, from Abu Hashim, the owner of the pomegranates, from Zadhan, from Ali ibn Abi Talib, who said: We entered with the Prophet, peace and blessings of Allah be upon him, upon a man from the Ansar who had a swelling. The Prophet, peace and blessings of Allah be upon him, said: "Will you not drain it for him?" He said: So it was lanced, and the Messenger of Allah, peace and blessings of Allah be upon him, was a witness.