The clarity of the Qur'an versus human refusal

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.