Allah's Messenger (ﷺ) said, "Do you consider or see that my face is towards the Qibla? By Allah, neither your submissiveness nor your bowing is hidden from me, surely I see you from my back."
Sahih al-Bukhari Book 8, Hadith 68
← Previous Hadith The Prophet (ﷺ) saw expectoration (on the wall of the mosque) in the direction of the Qibla and scraped it off with his hand. It seemed that he disliked it and the sign of disgust was apparent from his face. He said, "If anyone of you stands for the prayer, he is speaking in private to his Lord, (or) his Lord is between him and his Qibla, therefore he should not spit towards his Qibla, but he could spit either on his left or under his foot." Then he took the corner of his sheet and spat in it, folded it and said, "Or do this."

Sahih al-Bukhari Book 8, Hadith 67 Next Hadith → The Prophet (ﷺ) led us in a prayer and then got up on the pulpit and said, "In your prayer and bowing, I certainly see you from my back as I see you (while looking at you.)"

Sahih al-Bukhari Book 8, Hadith 69