Musnad Ahmad 32:342

Yahya ibn Adam narrated to us, Sufyan narrated to us, from Asim, from Yusuf ibn Abdullah ibn al-Harith, from Anas, who said: "The Messenger of Allah, peace and blessings of Allah be upon him, granted a concession regarding Ruqyah (incantations) for: the evil eye, the sting (of a venomous creature), and the Namlah (a skin ailment/ulcer)."