Musnad Ahmad 32:75

Ibn Abi ‘Adi narrated to us, from Humayd, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Let not one of you wish for death because of a harm that has befallen him. But let him say: 'O Allah, grant me life as long as life is better for me, and take my soul when death is better for me.'"