وَجَعَلۡنَا عَلَىٰ قُلُوبِهِمۡ أَكِنَّةً أَن يَفۡقَهُوهُ وَفِيٓ ءَاذَانِهِمۡ وَقۡرٗاۚ وَإِذَا ذَكَرۡتَ رَبَّكَ فِي ٱلۡقُرۡءَانِ وَحۡدَهُۥ وَلَّوۡاْ عَلَىٰٓ أَدۡبَٰرِهِمۡ نُفُورٗا

Wa izaa qara' tal Quraana ja'alnaa bainaka wa bainal lazeena laa yu'minoona bil aakhirati hijaabam mastooraa

And We put coverings over their hearts (and minds) lest they should understand the Qur'an, and deafness into their ears: when thou dost commemorate thy Lord and Him alone in the Qur'an, they turn on their backs, fleeing (from the Truth).

— Al-Isra' (ٱلْإِسْرَاء), 17:46