It was narrated that Anas said:"The Messenger of Allah said: 'Do not pray for death or wish for it. Whoever insists on praying for it let him say: Allahumma ahini ma kanatil-hayatu khairanli wa tawaffani idha kanatil-wafatu khairanli (O Allah, keep me alive so long as life is good for me, and cause me to die when death is good for me)

English translation · Sunan an-Nasa'i