Musnad Ahmad 1201:0

Narrated to us by 'Affan, who said: Narrated to us by Hammad ibn Salamah, from 'Asim ibn Bahdalah, from Abu Wa'il, from Shifa' bint 'Abd Allah, she said: The Messenger of Allah (peace be upon him) entered upon me while I was with Hafsah. He said to me: "Will you not teach this one the Ruqyah for skin eruptions (namlah) just as you taught her how to write?" She said: I said: "O Messenger of Allah, teach it to me." So he said: "Say: 'O Allah, Remover of harm, Lord of the people, heal, for You are the Healer. There is no healer but You, a healing that leaves behind no ailment.'"