Sunan Abu Dawud
683
Sahih+2

Abu Bakrah said that he came to the mosque when the prophet (ﷺ) was bowing. So I bowed outside the row (before joining it). The prophet (ﷺ) said; May Allah increase your eagerness! But do not do it again

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid