Musnad Ahmad 1086:8

'Abd al-Razzaq narrated to us, Ma'mar informed us, from al-Zuhri, from Haram ibn Muhayyisa, from his father, that he asked the Prophet, peace and blessings of Allah be upon him, about the earnings of a cupper. He forbade him. He repeated the question to him, and he forbade him. Then he mentioned his need to him, so he said: "Feed it to your camel used for drawing water, and feed it to your slaves."