When the Messenger of Allah ﷺ wanted to go to sleep, he put his right hand under his cheek and would then say three times: O Allah, guard me from Thy punishment on the day when Thou raisest up Thy servants. (Using translation from Abū Dāʾūd 5045)

أَنَّ الرَّسُولَ ﷺ كَانَ إِذَا أَرَادَ أَنْ يَرْقُدَ وَضَعَ يَدَهُ الْيُمْنَى تَحْتَ خَدِّهِ الْأَيْمَنِ وَقَالَ «اللهُمَّ قِنِي عَذَابَكَ يَوْمَ تَبْعَثُ عِبَادَكَ» ثَلَاثَ مَرَّاتٍ