وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًا ۚ وَإِذَا ذَكَرْتَ رَبَّكَ فِى ٱلْقُرْءَانِ وَحْدَهُۥ وَلَّوْا۟ عَلَىٰٓ أَدْبَـٰرِهِمْ نُفُورًا Qur’an Al-Israa (17:46)WajaAAalna AAala quloobihim akinnatan an yafqahoohu wafee athanihim waqran waitha thakarta rabbaka fee alqurani wahdahu wallaw AAala adbarihim nufooran
Cf. {6: 25}. See also 2:7 and the corresponding note.
Lit., "whenever thou dost mention in the Qur'an thy Sustainer alone".
The invisible veil being put against the ungodly on account of their deliberate rejection of Truth, the result is that their minds are fogged so that they cannot understand and their ears are clogged so that they cannot hear. In other words the effects of Evil become cumulative in shutting out Allah's grace.