Augustine of Hippo
When the book says, "And fire came down from God out of heaven and devoured them," we should not understand this as the final punishment that will come when it is said: "Depart from Me, you cursed, into the eternal fire prepared for the devil and his angels" (Mt 25:41).
For then they will be sent into the fire. Fire will not come down upon them from heaven.
Here it is fitting to understand by fire from heaven the very steadfastness of the saints, by which they will not yield to those committing cruelties and will not act according to their will.
For the firmament is heaven, and its firmness will make them suffer most cruelly from jealousy, since they will be unable to draw the saints of Christ to the side of the antichrist.
Read more (168 words)
This jealousy will be the fire that devours them, and it will be from God. For it is God's gift that the saints remain unconquered, thereby making their enemies suffer.
As it is said in a good sense, "Zeal for Thy house consumes me" (Ps 68:10), so it is said in the opposite sense: zeal has seized the people that hate, and now "fire will devour Thy enemies" (Isa 26:11).
It says "now," that is, apart from the fire of that final judgment.
But if the book called the blow by which the persecutors of the Church will be struck "fire descending from heaven and devouring them," then it refers to those whom Christ will find living on earth at His very coming.
Then "the lawless one will be revealed, whom the Lord Jesus will slay with the breath of His mouth" (2 Thess 2:8). Even this will not be the final punishment of the ungodly. That punishment will be what they undergo after the resurrection of bodies.