مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3622
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah (رضي الله عنه) said: I prayed one night with The Messenger of Allah (ﷺ) and he kept standing until I thought of doing something bad. We said: What was that? He said: I thought of sitting down and leaving him.
Musnad Ahmad 3646Its isnad is saheeh, al-Bukhari (1135) and Muslim (773)]