Sunan Ibn Majah
962
Sahih+3

It was narrated that Abu Musa said:“The Messenger of Allah (ﷺ) said: ‘I have gained weight, so when I bow, then bow, and when I stand up, then stand up, and when I prostrate, then prostrate. I should never find anyone preceding me in bowing or prostration.’”

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi