Revelation 20:8

And he will go out and deceive the nations, etc. Then he will deceive them to gather them for this battle. For even before, in the ways he could, he was deceiving through many and various evils. For it is said that he will go out: he will burst forth from the hidden places of his hatred into open persecution. Furthermore, Gog and Magog either signify the whole from a part or, according to the interpretation of their names, which are said to mean roof and from the roof, indicate hidden and open enemies. And they are the roof, because the enemy is now enclosed and ruled in them: and they will be from the roof when they erupt into open hatred.

In this passage "to deceive" means to scatter or to spoil, that is, to drag the nations along with him into condemnation, namely, all the wicked whom he has deceived in every part of the earth. And he will cause those who have been gathered together with him in one single condemnation to be delivered over to eternal torments. For Gog means "roof" and Magog means "out of the covering" or "out from the roof." Everyone whom he has brought out and led to the collapse of his own arrogance, or those whom he supported by the roof of his pride, or those who will be recognized as coming from the same cover and height of his arrogance, all these persons will be taken at the same time in one condemnation and by an eternal fire. When it says, "he will gather them for battle," it describes as something future what is in the past, for in some manner this battle is the hostility that the wicked have toward good works. And since those who are wicked are many and numerous, he adds, "whose number is like the sand of the sea."

Therefore, enough of these things. But since he said in what has gone before that the Devil will come forth to deceive the nations, he now says what nations and from whom they are gathered: He says, Gog and Magog, to gather them to the war. A war, however, against the saints. For having fulfilled the discourse concerning the salvific incarnation, he again returned from where he had gone out and related those things to us. He had gone forth from the Devil and the Antichrist; and from the defeat and punishment of the nations taken with them. Now I complete what was previously said insufficiently. He joins to the remaining nations those who have joined battle with the Antichrist; and Gog, thus saying: And he went out to deceive all the nations that are in the four corners of the earth; among whom he says also Gog and Magog, to gather them together to the war, whose number is like the sand of the sea. Concerning these, of Gog and of Magog, the prophetic seer Ezekiel delivered a prophecy, explaining how the wicked will be destroyed. These will be certain nations and rulers of nations gathered around the end (see Ezek. 38-39); for now they do not yet exist, or they are some of the nations now existing called by different names in the divine Scripture. These therefore will resist the God-hating Satan against the servants of Christ.