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." (Using translation from Bukhārī 6644)
"أتموا الركوعَ والسجود، فالذي نفسى بيده: إنَّى لأراكم من وراءِ ظهرى إذا ركعتم وإذا سجدتم".