Sunan Ibn Majah, Chapter: The Chapters on Medicine

"When the Messenger of Allah (saw) appointed me as governor of Ta'if, I began to get confused during my prayer, until I no longer knew what I was doing. When I noticed that, I travelled to the Messenger of Allah (saw), and he said: 'The son of Abul-'As?' I said: 'Yes, O Messenger of Allah.' He said: 'What brings you here?' He said: 'O Messenger of Allah, I get confused during my prayer, until I do not know what I am doing.' He said: 'That is Satan. Come here.' So I came close to him, and sat upon the front part of my feet then he struck my chest with his hand and put some spittle in my mouth and said: 'Get out, O enemy of Allah!' He did that three times, then he said: 'Get on with your work.'" 'Uthman said: "Indeed, I never felt confused (during my prayer) after that."