Musnad Abu Ya'la al-Mawsili 154:46

Zuhayr narrated to us, Isma'il narrated to us, from Khalid al-Hadhdha', from 'Abdullah ibn al-Harith, who said: When 'Abdullah ibn 'Umar would go to his bed, he would say: "O Allah, You created my soul and You take it; to You is its life and its death. O Allah, if You take it, then forgive it, and if You keep it alive, then protect it. O Allah, I ask You for well-being." A man from his children said to him: "O my father, did 'Umar use to say this?" He said: "Rather, someone better than 'Umar used to say it." He said: "So we thought that he meant the Prophet, may Allah bless him and grant him peace."