Musnad Ahmad 1227:14

Hashim narrated to us, he said: Abu Ma'shar narrated to us, from Yazid ibn Khusayfah, from 'Amr ibn Ka'b ibn Malik, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If one of you feels pain, let him place his hand where he feels the pain, then let him say seven times: 'I seek refuge in the might of Allah and His power over all things from the evil of what I feel.'"