John Chrysostom

"That the light of the Gospel of the glory of Christ should not dawn upon them." Not that they might disbelieve in God, but that unbelief might not see what are the things within, as also He enjoined us, commanding not to "cast the pearls before the swine." For had He revealed even to those who disbelieve, their disease would have been the rather aggravated. For if one compel a man laboring under ophthalmia to look at the sunbeams, he the rather increases his infirmity. …

Homily 8 on 2 Corinthians ↗

Theophylact of Ohrid

Having said above that although a veil lies upon the Israelites, we believers look with uncovered face, he now says that if the Gospel is veiled, it is veiled to unbelievers. For what was the case then with the Jews regarding Moses, the same thing now happens with unbelievers regarding the Gospel. But they themselves are to blame for this, not the Gospel, for if they had believed, they would have seen the glory of God without a veil.

Commentary on 2 Corinthians ↗

Thomas Aquinas

Here the Apostle answers a tacit objection. For someone could say to him: you say that you do not grow faint in manifesting the truth of Christ. But this does not seem true, because many people contradict you. To this question, therefore, he responds. And in regard to it he does two things: first, he responds to this question; secondly, he removes a doubt which seems to follow from his answer (v. 5). In regard to the first he does three things. …

Commentary on 2 Corinthians ↗