ذَٰلِكَ

بِأَنَّهُمۡ

ءَامَنُواْ

ثُمَّ

كَفَرُواْ

فَطُبِعَ

عَلَىٰ

قُلُوبِهِمۡ

فَهُمۡ

لَا

يَفۡقَهُونَ

٣

That is because they declared faith (in Islam apparently), then disbelieved (secretly). Therefore a seal has been set on their hearts, and thus they do not understand.