Perform bowing and prostration well. By Allah, I see you even if you are behind me, or he said: (I see you) behind my back when you bow or prostrate.
Sahih Muslim Book 4, Hadith 121
← Previous Hadith The Messenger of Allah (ﷺ) said: Do you find me seeing towards the Qibla only? By Allah, your bowing and your prostrating are not hidden from my view. Verily I see them behind my back.

Sahih Muslim Book 4, Hadith 120 Next Hadith → The Apostle of Allah (ﷺ) said: Complete the bowing and prostration well. By Allah, I see you behind my back as to how you bow and prostrate or when you bow and prostrate.

Sahih Muslim Book 4, Hadith 122