Surat Al-Israa (The Night Journey) - الإسراء

وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًا وَإِذَا ذَكَرْتَ رَبَّكَ فِى ٱلْقُرْءَانِ وَحْدَهُۥ وَلَّوْا۟ عَلَىٰٓ أَدْبَٰرِهِمْ نُفُورًا ﴿٤٦﴾

And We have placed coverings on their hearts and a heaviness in their ears lest they understand it, and when you mention your Lord alone in the Quran they turn their backs in aversion.