The Messenger of Allah ﷺ said, "Do you think my qiblah is only here in front of me? By Allah, neither your humility nor your bowing is hidden from me. I can see you from behind my back."
حدثنا إسحاق بن عيسى حدثنا مالك عن أبي الزناد عن الأعرج
أن رسول الله ﷺ قال هل ترون قبلتي هاهنا فوالله ما يخفى علي خشوعكم ولا ركوعكم إني لأراكم من وراء ظهري
Its isnad is sahih. It has already occurred at 8011, and it appears in Bukhari 1/114, in the Book of Prayer, in the chapter on the imam admonishing people to complete the prayer properly, and in Muslim 1/319, number 424, in the Book of Prayer, in the chapter on the command to improve the prayer.