Or the meaning is, that disbelief itself is the punishment of the impenitent: inasmuch as that is to be without light, and to be without light is of itself the greatest punishment. Or He is announcing what is to be. Though a murderer be not yet sentenced by the Judge, still his crime has already condemned him. In like manner he who believes not, is dead, even as Adam, on the day that he ate of the tree, died.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom. xxviii. 1