The Messenger of Allah ﷺ said, "Do you think my prayer direction is only here in front of me? By Allah, your humility and your bowing are not hidden from me. I see you from behind my back."
أن رسول الله ﷺ قال: أترون قبلتي هاهنا؟ فو الله ما يخفى علي خشوعكم ولا ركوعكم، إني لأراكم من وراء ظهري.
Malik narrated it, from Abu Zinad, from Araj, from Abu Hurairah, who mentioned it. Bukhari related it in the Book of Prayer (418) and Muslim in the Book of Prayer (424:109), both through the route of Malik with the same chain.In a narration of Muslim (423:108), Abu Hurairah said, "The Messenger of Allah ﷺ led us in prayer one day, then when he finished he said, 'O so-and-so, will you not perfect your prayer? Should not the one praying consider, when he prays, how he prays? For he is only praying for himself. By Allah, I can see behind me just as I see in front of me.'"