Musnad Ahmad 1153:821

Muhammad ibn Sabiq narrated to us, he said: Ibrahim ibn Tahman narrated to us, from Mansur, from Ibrahim ibn Yazid, from Masruq, and Abu al-Duha, from Masruq, from Aisha, that she said: When the Messenger of Allah, peace and blessings of Allah be upon him, was brought a sick person, he would say: "Remove the harm, O Lord of the people, and heal, for You are the Healer. There is no healing except Your healing, a healing that leaves behind no illness."