Musnad Ahmad 5:76

Yahya narrated to us, from Shu'bah, who said: 'Amr ibn Murrah narrated to us, from 'Abdullah ibn Salamah, from 'Ali, who said: The Messenger of Allah (peace and blessings of Allah be upon him) passed by me while I was in pain, and I was saying: "O Allah, if my time has come, then grant me rest; and if it is delayed, then raise me up; and if it is a trial, then grant me patience." He said: "What did you say?" So I repeated it to him. He struck me with his foot and said: "What did you say?" He said: So I repeated it to him. He then said: "O Allah, grant him wellness, or heal him." He said: I never suffered from that pain again.