Tafseer Ibn Kathir of YAA SIIN [9]

وَجَعَلْنَا مِن بَيْنِ أَيْدِيهِمْ سَدًّا وَمِنْ خَلْفِهِمْ سَدًّا فَأَغْشَيْنَاهُمْ فَهُمْ لاَ يُبْصِرُونَ

And We have put before them a barrier and behind them a barrier and covered them, so they do not see.