Musnad Ahmad 27:1053

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Khalid, Abdullah ibn al-Harith narrated to us, from Abdullah ibn Umar, that he commanded a man that when he took to his bed, he should say: "O Allah, You created my soul, and You take it back. To You is its death and its life. If You keep it alive, then protect it, and if You cause it to die, then forgive it. O Allah, I ask You for well-being." A man said: "Did you hear this from Umar?" He replied: "From one better than Umar, from the Messenger of Allah, may Allah bless him and grant him peace."