(3) باب كَيْفَ كَانَتْ يَمِينُ النَّبِيِّ صلى الله عليه وسلم
Narrated Anas bin Malik:
I heard the Prophet (ﷺ) saying, "Perform the bowing and the prostration properly (with peace of mind), for, by Him in Whose Hand my soul is, I see you from behind my back when you bow and when you prostrate."
Reference: Sahih al-Bukhari 6644
In-book reference: Book 83, Hadith 23
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 8, Book 78, Hadith 639