مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3773
Musnad of Abdullah bin Mas'ood
It was narrated from ‘Abdullah (رضي الله عنه) from the Prophet (ﷺ) that When he went to sleep, he would put his right hand under his cheek and say: "O Allah, protect me from Your punishment on the Day when You gather Your slaves together.”
Musnad Ahmad 3796Saheeh because of corroborating evidence, this is a da'eef i