The clarity of the Qur'an

وَكَذَٰلِكَ أَنزَلْنَـٰهُ حُكْمًا عَرَبِيًّا ۚ وَلَئِنِ ٱتَّبَعْتَ أَهْوَآءَهُم بَعْدَ مَا جَآءَكَ مِنَ ٱلْعِلْمِ مَا لَكَ مِنَ ٱللَّهِ مِن وَلِىٍّ وَلَا وَاقٍ

And thus We have revealed it as an Arabic legislation. And if you should follow their inclinations after what has come to you of knowledge, you would not have against Allāh any ally or any protector.

وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًا ۚ وَإِذَا ذَكَرْتَ رَبَّكَ فِى ٱلْقُرْءَانِ وَحْدَهُۥ وَلَّوْا۟ عَلَىٰٓ أَدْبَـٰرِهِمْ نُفُورًا

And We have placed over their hearts coverings, lest they understand it, and in their ears deafness. And when you mention your Lord alone in the Qur’ān, they turn back in aversion.