Hardening of hearts and spiritual blindness

إِنَّ ٱلَّذِينَ ءَامَنُوا۟ ثُمَّ كَفَرُوا۟ ثُمَّ ءَامَنُوا۟ ثُمَّ كَفَرُوا۟ ثُمَّ ٱزْدَادُوا۟ كُفْرًا لَّمْ يَكُنِ ٱللَّهُ لِيَغْفِرَ لَهُمْ وَلَا لِيَهْدِيَهُمْ سَبِيلًۢا

Indeed, those who have believed then disbelieved, then believed then disbelieved, and then increased in disbelief - never will Allāh forgive them, nor will He guide them to a way.