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)”"
Sahih IsnaadSahih IsnaadSahih - Agreed UponBook 21 · Hadith 5