Revelation 16:9

These plagues from God do not strike them in the body but in the soul. And, therefore, they do not consider God but progress toward greater evil and for that reason blaspheme [God] and persecute his saints.

It is not given to the sun, but to that angel who poured out [the bowl] on the sun [to scorch people]. This fire is not to be regarded as that of Gehenna, for there no opportunity for blasphemy remains for anyone, when for the damned any attempt at repentance will be fruitless. And so the law says that they will say, “What has our arrogance profited us? And what good has the boast of our wealth brought to us?” Therefore, I think that in this passage the fire and the heat ought be interpreted to mean that the body of the devil is irremediably tormented by the steadfastness of the saints, and aroused by the heat, [he] is led to blasphemy. For perhaps it says “on the sun” in the sense of “by the sun,” as if he had put the sun in the ablative case, referring in this case to the “sun of righteousness.” We have such readings; for example, “I shall watch over my word to perform it,” and in Daniel, “Let us seek mercy from God Almighty over this mystery.” And so, from where the elect receive the steadfastness of their illumination, from there the wicked are said to obtain fire.

It is the habit of blasphemers that they prefer to blame God for wickedness and iniquity rather than themselves, and therefore [they] do not seek penance after plagues but, even though tormented, continue to throw insults. For just as a bronze vase, when subjected to a great fire, brings up bubbles from the inside that boil up on the outside and exceed its own capacity, so also those who belong to the beast, resisting the Unconquered, see the church of Christ struggle with a tireless constancy, and inflamed by the flames of an intolerable envy, exhale a fire conceived in the heart through the blasphemies of an impure mouth.

Perhaps humankind will literally be burned by the fierce heat of the sun. While God in his goodness “curbs them with bit and bridle who do not draw near to him” so that they might look toward repentance, some have fallen to such depths of evil that by the depravity of their minds they will not turn to conversion but rather to blasphemy. Perhaps, however, the image of the sun signifies the course of the day that burns those worthy of scourging by the heat of temptations, so that by the experience of sufferings they might learn to hate the mother of these things, namely, sin. However, those who are mindless concerning any knowledge of their own faults will “sharpen their tongue” against God, just as even now we see many who are distressed by the unspeakable horrors that encompass us at the hands of the barbarians and who blame the goodness of God, since he has held such evils for our own generation.

And men were scorched with great heat. At present, indeed, as much as is permitted, the devil glorifies his own. But that clarity and joy the Holy Spirit has defined as plagues and sorrows. For we read above that the army of the devil killed men by fire, smoke, and brimstone. Not that he clearly killed them, but that he destined those who consented to these punishments.

These men also blasphemed and, he says, did not repent. And therefore the plagues, so that since through the benefits of God they did not know the Master, at least through punishments they may come to recognition.