Muwatta Malik #1846

Yahya related to me from Malik from Yazid ibn Khusayfa that Amr ibn Abdullah ibn Kab as-Salami told him that Nafi ibn Jubayr told him that Uthman ibn Abi al-As came to the Messenger of Allah, may Allah bless him and grant him peace. Uthman said that he had a pain which was enough to kill him. The Messenger of Allah, may Allah bless him and grant him peace, said, "Rub it with your right hand seven times and say, 'I take refuge with the might of Allah and His power from the evil of what I feel.' " Uthman added, "I said that, and Allah removed what I had. I still command my family and others to say it."