Musnad Ahmad 658:120

Yahya ibn Adam narrated to us, Fudayl—meaning Ibn Iyad—narrated to us, from Mansur, from Sa'd ibn Ubaydah, from al-Bara' ibn 'Azib, from the Prophet, peace and blessings of Allah be upon him, who said: "When you go to your bed, perform ablution, lie on your right side, and say: 'O Allah, I have submitted my face to You, entrusted my affair to You, and relied upon You for support, out of fear and hope in You. There is no refuge and no escape from You except to You. I have believed in Your Book which You revealed, and in Your Prophet whom You sent.' For if you die, you will die upon the natural disposition (fitrah)."