Musannaf Ibn Abi Shayba 13:1026

Abu Bakr narrated to us, he said: Ibn Abi Za’idah narrated to us, from Ash’ath, from Ibn Sirin, from Ibn Abbas, who said: The Prophet, peace and blessings of Allah be upon him, was cupped and he paid the cupper. If it were forbidden, he would not have given it to him.