﴿ كَذَٰلِكَ يَطْبَعُ ٱللَّهُ عَلَىٰ قُلُوبِ ٱلَّذِينَ لَا يَعْلَمُونَ ﴾

“In this way does God seal the hearts of those who do not [want to] know [the truth].”

(Thus doth Allah seal the hearts of those who know not) Allah's divine Oneness and disbelieve in it.