Whenever the Prophet ﷺ visited a sick person, he would say, "Allah, remove the affliction, Lord of mankind, and grant healing, for You are the Healer. There is no healing but Your healing, a healing that leaves no illness behind."
حدثنا سفيان بن وكيع حدثنا يحيى بن آدم عن إسرائيل عن أبي إسحق عن الحارث
كان النبي ﷺ إذا عاد مريضا قال اللهم أذهب البأس رب الناس واشف فأنت الشافي لا شفاء إلا شفاؤك شفاء لا يغادر سقما
[Sahih]. Ahmad (1/66) also reported it through Israil, with the same chain, and its chain of transmission is daif. The hadith has corroborating narrations in Bukhari (5675) and Muslim (3191) and others.