Quran

 47:24

أَفَلَا يَتَدَبَّرُونَ الْقُرْآنَ أَمْ عَلَىٰ قُلُوبٍ أَقْفَالُهَا ﴿٢٤﴾

24. Do they not contemplate the Quran? Or do hearts have their locks upon them?