مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4025
Musnad of Abdullah bin Mas'ood
It was narrated from 'Abdullah that The Messenger of Allah (ﷺ) used to sleep on his back until he breathed deeply, then he would get up and pray and would not do wudoo’.
Musnad Ahmad 4051A saheeh hadeeth; this is a da'eef isnad because al-Hajjaj -