Hadith 418
Narrated Abu Huraira: Allah's Apostle 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."
Hadith 419
Narrated Anas bin Malik: The Prophet 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.)"