Sunan an Nasai
1821
Sahih+2

It was narrated that Anas said:"The Messenger of Allah said: 'None of you should wish for death because of some harm that befalls him. If he must wish for death, let him say: Allahumma ahini ma kanatil-hayatu khairantli 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)

SahihAbu Ghuddah
SahihAl-Albani