Shama-il Tirmidhi Chapter 38, Hadith Number 1 (242).
Baraa Radiyallahu ‘Anhu reports: “When Rasulullah Sallallahu ‘Alayhi Wasallam retired, he put his right hand under his right cheek, and recited this du’aa: Rabbi qini adhaa-baka yauma tub-a-thu ‘ibaadaka. Translation…  O Allah, save me from Your punishment on the day…