Musannaf Ibn Abi Shayba 21:727

Ubayd Allah ibn Musa narrated to us, from Isra'il, from Abu Ishaq, from Asim, from Ali, who said: He used to say when going to sleep, if he slept: "In the name of Allah, and in the way of Allah, and upon the religion of the Messenger of Allah, may Allah bless him and grant him peace." And he would say it when a man was placed into his grave.