Musannaf Ibn Abi Shayba 21:176

Ghundar narrated to us, from Shu'bah, from 'Amr ibn Murrah, from Sa'd ibn 'Ubaydah, from al-Bara' ibn 'Azib, from the Prophet (may Allah bless him and grant him peace), that he said to a man: "When you take to your bed, say: 'O Allah, I have submitted my soul to You, and I have turned my face toward You, and I have entrusted my affair to You, and I have leaned my back upon You, out of desire and fear. There is no refuge and no shelter from You except with You. I have believed in Your Book which You revealed, and Your Prophet whom You sent.' For if you die, you will die upon the natural disposition (fitrah)."