Surat Al-'Isrā' - سورة الإسراء

وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِي آذَانِهِمْ وَقْرًا ۚ وَإِذَا ذَكَرْتَ رَبَّكَ فِي الْقُرْآنِ وَحْدَهُ وَلَّوْا عَلَىٰ أَدْبَارِهِمْ نُفُورًا

Muhsin Khan: And We have put coverings over their hearts lest, they should understand it (the Quran), and in their ears deafness. And when you make mention of your Lord Alone [La ilaha ill-Allah (none has the right to be worshipped but Allah) Islamic Monotheism ] in the Quran, they turn on their backs, fleeing in extreme dislikeness.