﴿ وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًۭا ۚ وَإِذَا ذَكَرْتَ رَبَّكَ فِى ٱلْقُرْءَانِ وَحْدَهُۥ وَلَّوْا۟ عَلَىٰٓ أَدْبَٰرِهِمْ نُفُورًۭا ﴾

“for, over their hearts We have laid veils which prevent them from grasping its purport, and into their ears, deafness. And so, whenever thou dost mention, while reciting the Qur'an, thy Sustainer as the one and only Divine Being, they turn their backs [upon thee] in aversion.”

And We place upon their hearts veils covers lest they should understand it lest they should understand the Qur’ān in other words and so in this way they do not understand it and in their ears a deafness a heaviness thus they cannot hear it. And when you mention your Lord alone in the Qur’ān they turn their backs in aversion to it.