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)WajaAAaln a AAal a quloobihim akinnatan an yafqahoohu wafee atha nihim waqran wai tha th akarta rabbaka fee alqur a ni wa h dahu wallaw AAal a adb a rihim nufoor a n
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.