Allah commands the People of the Scriptures to believe in what He has sent down to His servant and Messenger, Muhammad , the Glorious Book that conforms to the good news that they already have about Muhammad . He also warns them,

﴿مِّن قَبْلِ أَن نَّطْمِسَ وُجُوهاً فَنَرُدَّهَا عَلَى أَدْبَـرِهَآ﴾

(before We efface faces and turn them backwards) Al-`Awfi said that Ibn `Abbas said that `effacing' here refers to blindness,

﴿فَنَرُدَّهَا عَلَى أَدْبَـرِهَآ﴾

(and turn them backwards) meaning, We put their faces on their backs, and make them walk backwards, since their eyes will be in their backs. Similar was said by Qatadah and `Atiyah Al-`Awfi. This makes the punishment even more severe, and it is a parable that Allah set for ignoring the truth, preferring the wrong way and turning away from the plain path for the paths of misguidance. Therefore, such people walk backwards. Similarly, some said that Allah's statement,

﴿إِنَّا جَعَلْنَا فِى أَعْنـقِهِمْ أَغْلَـلاً فَهِىَ إِلَى الاٌّذْقَـنِ فَهُم مُّقْمَحُونَ وَجَعَلْنَا مِن بَيْنِ أَيْدِيهِمْ سَدّاً﴾

(Verily, We have put on their necks iron collars reaching to the chins, so that their heads are raised up. And We have put a barrier before them) that is a parable that Allah gave for their deviation and hindrance from guidance.