63:3
ذَٰلِكَ بِأَنَّهُمْ ءَامَنُوا۟ ثُمَّ كَفَرُوا۟ فَطُبِعَ عَلَىٰ قُلُوبِهِمْ فَهُمْ لَا يَفْقَهُونَ
dhālika bi-annahum āmanū thumma kafarū faṭubiʿa ʿalā qulūbihim fahum lā yafqahūna
because they professed faith and then rejected it, so their hearts have been sealed and they do not understand.
That is because they believed, and then disbelieved; therefore their hearts are sealed, so they understand not.