مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3950
Musnad of Abdullah bin Mas'ood
It was narrated that ‘Abdullah said: The Messenger of Allah (ﷺ) offered a prayer, and I do not know whether he added something or omitted something, then he said the salam and prostrated twice.
Musnad Ahmad 3975Its isnad is saheeh, Muslim (527)]