Musnad Ahmad 32:812

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, he said: I heard ‘Ali ibn Zayd saying: I heard Anas narrating from the Prophet, may Allah bless him and grant him peace, that he said: "The believer—or he said: one of you—should not wish for death. If he must do so, then 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.'"