Hudhaifah (May Allah be pleased with him) reported

Whenever the Messenger of Allah (ﷺ) intended to go to sleep, he would place his right hand under his (right) cheek and supplicate: "Allahumma qini 'adhabaka yauma tab'athu 'ibadaka (O Allah! Guard me against Your punishment on the Day when You will resurrect Your slaves)."

[At-Tirmidhi].

In a narration in Abu Dawud, Hafsah (May Allah be pleased with her) said: Before going to sleep the Messenger of Allah (ﷺ) would recite this Du'a three times.