Sahih Muslim
The Book on Salutations and Greetings (Kitab As-Salam)
Book Number: 026 / Hadith Number: 5434
'A'isha reported Allah's Messenger (may peace be upon him) as saying: When Allah's Messenger (may peace be upon him) visited the sick he would say: Lord of the people. remove the disease, cure him, for Thou art the great Curer, there is no cure but through Thine healing Power, which leaves nothing of the disease.