"The Messenger of Allah ﷺ was ill, and we prayed behind him while he was sitting, and Abu Bakr repeated his takbirs so that the people could hear them. He turned to us and saw us standing, so he gestured to us to sit down. So we prayed behind him sitting. When he said the salam he said: 'Just now you were doing what the Persians and Romans do for their kings when they are sitting. Do not do that. Follow your Imams: If they pray standing then pray standing, and if they pray sitting then pray sitting.'"  

أَنَّهُ قَالَ اشْتَكَى رَسُولُ اللَّهِ ﷺ فَصَلَّيْنَا وَرَاءَهُ وَهُوَ قَاعِدٌ وَأَبُو بَكْرٍ يُكَبِّرُ يُسْمِعُ النَّاسَ تَكْبِيرَهُ فَالْتَفَتَ إِلَيْنَا فَرَآنَا قِيَامًا فَأَشَارَ إِلَيْنَا فَقَعَدْنَا فَصَلَّيْنَا بِصَلاَتِهِ قُعُودًا فَلَمَّا سَلَّمَ قَالَ إِنْ كُنْتُمْ آنِفًا تَفْعَلُونَ فِعْلَ فَارِسَ وَالرُّومِ يَقُومُونَ عَلَى مُلُوكِهِمْ وَهُمْ قُعُودٌ فَلاَ تَفْعَلُوا ائْتَمُّوا بِأَئِمَّتِكُمْ إِنْ صَلَّى قَائِمًا فَصَلُّوا قِيَامًا وَإِنْ صَلَّى قَاعِدًا فَصَلُّوا قُعُودًا  

"The Messenger of Allah ﷺ used to turn to his right and left when praying, but he did not twist his neck to look behind him."  

كَانَ رَسُولُ اللَّهِ ﷺ يَلْتَفِتُ فِي صَلاَتِهِ يَمِينًا وَشِمَالاً وَلاَ يَلْوِي عُنُقَهُ خَلْفَ ظَهْرِهِ