Musnad Ahmad 5:131

Abu al-Nadr Hashim and Abu Dawud narrated to us, they said: Warqa’ informed us, from ‘Abd al-A’la al-Tha’labi, from Abu Jamila, from ‘Ali, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) was cupped, and he ordered me to give the cupper his wage."