Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrated: When the Messenger of Allah (peace and blessings be upon him) went to sleep, he would place his right hand under his right cheek and say: "O my Lord, protect me from Your punishment on the day You resurrect Your servants."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10048