Messenger of Allah 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."  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ هَلْ تَرَوْنَ قِبْلَتِي هَا هُنَا فَوَاللَّهِ مَا يَخْفَى عَلَىَّ خُشُوعُكُمْ وَلاَ رُكُوعُكُمْ إِنِّي لأَرَاكُمْ مِنْ وَرَاءِ ظَهْرِي  

The Prophet ﷺ said, "Perform the bowing and the prostrations properly. By Allah, I see you from behind me (or from behind my back) when you bow or prostrate."  

عَنِ النَّبِيِّ ﷺ قَالَ أَقِيمُوا الرُّكُوعَ وَالسُّجُودَ فَوَاللَّهِ إِنِّي لأَرَاكُمْ مِنْ بَعْدِي وَرُبَّمَا قَالَ مِنْ بَعْدِ ظَهْرِي إِذَا رَكَعْتُمْ وَسَجَدْتُمْ