Musannaf Ibn Abi Shayba 13:1028

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Abu Janab narrated to us, from Abu Jamila al-Tuhawi, he said: I heard Ali saying: The Messenger of Allah (peace and blessings of Allah be upon him) was cupped. Then he said to the cupper when he finished: "What is your fee?" He said: "Two sa’s." He said: So he remitted one sa’ for him. He said: Then he commanded me, and I gave him one sa’.