Musnad Ahmad 30:1393

'Affan narrated to us, Hammad ibn Salamah narrated to us, Muhammad ibn 'Amr narrated to us, from Abu Salamah, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "If there is any good in anything you use for medical treatment, it is in cupping (al-hijamah)."