The Quran as a test and criterion (furqān)

وَأَمَّا ٱلَّذِينَ فِى قُلُوبِهِم مَّرَضٌ فَزَادَتْهُمْ رِجْسًا إِلَىٰ رِجْسِهِمْ وَمَاتُوا۟ وَهُمْ كَـٰفِرُونَ

But as for those in whose hearts is disease, it has [only] increased them in evil [in addition] to their evil. And they will have died while they are disbelievers.