Musnad Ahmad 299:1

Rawh narrated to us, he said: Malik ibn Anas narrated to us, from Yazid ibn Khusayfah, that ‘Amr ibn ‘Abd Allah ibn Ka‘b al-Sulami informed him, that Nafi‘ ibn Jubayr informed him, that ‘Uthman ibn Abi al-‘As came to the Messenger of Allah, may Allah bless him and grant him peace. ‘Uthman said: "And there was a pain in me that had almost destroyed me." The Messenger of Allah, may Allah bless him and grant him peace, said: "Place your right hand [on it] seven times, and say: 'I seek refuge in the might of Allah and His power from the evil of what I find.'" He said: "So I did that, and Allah took away what I had. And I have not ceased commanding my family and others to do it."