وَجَعَلنا عَلىٰ قُلوبِهِم أَكِنَّةً أَن يَفقَهوهُ وَفي آذانِهِم وَقرًا ۚ وَإِذا ذَكَرتَ رَبَّكَ فِي القُرآنِ وَحدَهُ وَلَّوا عَلىٰ أَدبارِهِم نُفورًا

We placed covers on their hearts, preventing them from understanding it, and deafness in their ears. When you mention your Lord’s singularity in the Quran, they recoil in repulsion.