Musnad Ahmad 1153:2244

Ishaq ibn Isa narrated to us, he said: Malik informed us, from al-Zuhri, from Urwah, from Aisha: "That the Messenger of Allah, peace and blessings of Allah be upon him, when he was ill, would recite the Mu'awwidhat (the chapters of seeking refuge) over himself and blow. When his pain intensified, I would recite over him and wipe him with his own hand, hoping for its blessing."