مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2307
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn 'Abbas (رضي الله عنه) that the Prophet (ﷺ) said: "The one who falls asleep whilst prostrating is not required to do wudoo’, unless he lies down. If he lies down, then his muscles relax."
Musnad Ahmad 2315Its isnad is da'eef]