Musnad Ahmad 25:1120

Hashim narrated to us, Israel narrated to us, from Jabir, from 'Amir, from Ibn 'Abbas, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) was cupped and gave the cupper his wage. Had it been forbidden, he would not have given it to him. He used to be cupped on the two jugular veins and between the shoulders. A slave of the Banu Bayada used to cup him, and a mudd and a half [of grain] was taken from him every day. The Prophet (peace and blessings of Allah be upon him) interceded for him with his masters, so they made it a mudd."