The Messenger of Allah ﷺ said: "Bow and prostrate properly, for by Allah (SWT) I can see you from behind my back when you bow and prostrate."  

عَنْ رَسُولِ اللَّهِ ﷺ قَالَ أَتِمُّوا الرُّكُوعَ وَالسُّجُودَ فَوَاللَّهِ إِنِّي لأَرَاكُمْ مِنْ خَلْفِ ظَهْرِي فِي رُكُوعِكُمْ وَسُجُودِكُمْ