One day the Messenger of Allah ﷺ led the prayer. Then turning (towards his Companions) he said: O you man, why don't you say your prayer well? Does the observer of prayer not see how he is performing the prayer, for he performs it for himself? By Allah, I see behind me as I see in front of me.  

صَلَّى بِنَا رَسُولُ اللَّهِ ﷺ يَوْمًا ثُمَّ انْصَرَفَ فَقَالَ يَا فُلاَنُ أَلاَ تُحْسِنُ صَلاَتَكَ أَلاَ يَنْظُرُ الْمُصَلِّي إِذَا صَلَّى كَيْفَ يُصَلِّي فَإِنَّمَا يُصَلِّي لِنَفْسِهِ إِنِّي وَاللَّهِ لأُبْصِرُ مَنْ وَرَائِي كَمَا أُبْصِرُ مَنْ بَيْنَ يَدَىَّ  

The Messenger of Allah ﷺ said: Do you find me seeing towards the Qibla only? By Allah, your bowing and your prostrating are not hidden from my view. Verily I see them behind my back.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ هَلْ تَرَوْنَ قِبْلَتِي هَا هُنَا فَوَاللَّهِ مَا يَخْفَى عَلَىَّ رُكُوعُكُمْ وَلاَ سُجُودُكُمْ إِنِّي لأَرَاكُمْ وَرَاءَ ظَهْرِي  

Perform bowing and prostration well. By Allah, I see you even if you are behind me, or he said: (I see you) 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  

The Apostle of Allah ﷺ said: Complete the bowing and prostration well. By Allah, I see you behind my back as to how you bow and prostrate or when you bow and prostrate.  

أَنَّ نَبِيَّ اللَّهِ ﷺ قَالَ أَتِمُّوا الرُّكُوعَ وَالسُّجُودَ فَوَاللَّهِ إِنِّي لأَرَاكُمْ مِنْ بَعْدِ ظَهْرِي إِذَا مَا رَكَعْتُمْ وَإِذَا مَا سَجَدْتُمْ وَفِي حَدِيثِ سَعِيدٍ إِذَا رَكَعْتُمْ وَإِذَا سَجَدْتُمْ