Surah 9. Al-Tawba, Ayah 125

Lit., "it but adds [another] loathsome evil to their loathsome evil" - i.e., makes them more stubborn in their denying the truth of God's messages because they are a priori determined to deny everything that is incompatible with their refusal to admit the existence of anything that is beyond the reach of human perception (al-ghayb - see surah {2}, note [3]).

 i.e., hypocrites.

Cf. ii. 10 and several similar passages. Just as the light, which to healthy eyes gives enlightenment, causes pain to the diseased eye, which emits unclean matter, so to those spiritually diseased. Allah's grace is unwelcome, and they put forth more doubts to cover their disease. And they die in their disease, and of their discase. Note the aptness of the metaphor.