Allāhumma qini ‘adhābaka yawma tajma‘u or tab‘athu ‘ibādak (O Allah, protect me from Your punishment on the Day You gather or resurrect Your servants)

When the Prophet (may Allah's peace and blessings be upon him) lay down to sleep, he would rest his head on his right hand and place his right cheek upon it, and he would say: "O Allah" my Lord, "protect me" and guard me against "Your punishment" and torment "on the Day You gather or resurrect Your servants" for reckoning, i.e., the Day of Judgment.