Oecumenius

For they willingly do not know that the heavens were of old, and the earth standing out of the water and in the water by the word of God: by which the world that then was, being overflowed with water, perished. But the heavens and the earth which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men.
And what is it that they do not know? That just as in the flood, the heavens were from the water according to the creation of the world narrated by Moses: (for he himself says that God commanded that a firmament be made in the midst of the waters (Gen. 1:6), that is, a firmer substance than the waters): so also the earth appeared from the waters at the command of the Creator, which had also been submerged at first. And just as the flood unexpectedly came upon the heavens and the earth constituted from water, so it has now been established that the corruption of the universe will occur through fire, with which the wicked will also perish. Since these two elements, water and fire, were created along with the universe, from which the other two elements are also derived: air indeed from the evaporated waters, but the earth from the compacted ones: namely, just as it was made from fire through evaporation and compression, with no one who has a mind objecting (for this virtue has been bestowed upon fire by God the Creator), since these two, I say, have always existed in this way, and previously the destruction of the wicked was made through water, it is necessary that the destruction of those who act wickedly will again occur through fire. Moreover, that the corruption of this universe is evident not only to Christians but also to the wise men of the Greeks, as is the case with Heraclitus of Ephesus and Empedocles of Etna12. But someone might say: And what is the reason for its creation if the world must again be reduced to nothingness? And we will say that the world does not tend entirely towards corruption, but towards renewal; therefore, the Prophet also says: "And you will renew the face of the earth." (Ps. 103:32) For just as the creation, being from God from the beginning, was good, and not merely good by chance: through the transgression of man, the creation itself became subject to vanity, that is, not having a firm existence, but being in a state of instability and change.
Then in the flood, when few men had persevered in divine worship, the world again seemed to take on the beginning of its reconstruction through Noah and those who had been saved in the ark along with the animals for the establishment of seeds: nevertheless, even then, human nature did not persist in its previous state, but rather declined to worse conditions than those that had existed before, from which neither the law given by Moses turned them away, nor the presence of the Lord, except that a few turned aside to those things which led to salvation. For how great is the multitude of those who are saved if you compare it to the multitude of those who perish, who are generated daily? For this reason, it seems to me that the time of fulfillment is delayed until the number of the saved is completed. Therefore, since the call to salvation has been made in various ways, and the destruction from unbelief is diverse: for this reason, a cataclysmic fire is necessary, indeed a destruction, although not entirely perfect: not indeed of souls, but neither of bodies. For we must all be revealed before the tribunal of Christ (2 Cor. 5:10), not with our souls naked, but together with our bodies, and with them incorruptible. For how could a naked soul account for those things which have been done through the body? Indeed, it is not the part of a just judge, when two have sinned in the same way, to dismiss one and transfer the whole crime to the other. Furthermore, if we are accustomed to melt certain corporeal things again with fire, not to attribute to them absolute destruction, but to provide them with purity and sincerity: let no one doubt that God, who has promised completion through fire, will either not bring about corruption, or will indeed do so in such a way that through the corruption of one, He makes another. But even if it were to corrupt, what would it corrupt? The superfluous and those related to present life: and what are those? Beasts, herbs, plants. Indeed, herbs are for the beasts, and the beasts are for the service of this corruptible life. "Producing," he says, "hay for the beasts and herbs for the service of men." (Ps. 103:14) As for the plants, some are indeed for covering and for building houses, while others are for providing food. Moreover, the fact that animals require food is a sign of corruption. For what else could the middle and fullness provide but corruption? Therefore, those things which are superfluous to immortal life would be corrupted. But He will create new heavens and a new earth (Isa. 65:17), not another in terms of material. For even one who builds a new house does not indeed make it from non-existing material. Thus, God created the material and shaped it from the beginning, as much as was certainly necessary for the use of that time.
To the incorruptibility, however, which will corrupt that which is useless and unnecessary after the present state. If something is useful, it will allow for an improvement with immortal and incredible beauty, so as to perfect and complete another and incorruptible world.
"and the earth standing out of the water." The earth indeed from water as from a material principle, but through water as through a perfecting principle. For water contains the earth like a certain glue that is to it; unless it were to touch it, it would necessarily dissolve and be carried into the air. However, perhaps someone will approach us with vain thought saying: For what reason did God, who produced this visible world, not create it firm and unchangeable from the beginning, but subject to changes? Hence, it was also immediately necessary to be restored, indeed at the time of Noah through water, but reserved unto fire, as Peter now says? To which we will say that it was not possible for it to have changelessness.
How indeed, for he who has received his being from change? If indeed it was produced from non-being to being, which no wise person would say is not a change. And in what way has the change progressed to worse, mixed with worse, it was necessary for this Creator to restore it to better; indeed, at the time of Noah he purified through water, but in the end he will do so through fire. Just as we are accustomed to melt certain material things again with fire, not for destruction, but for purification.
"by which," namely heaven and earth, indeed submerged by waters, but the heavens sending down their gushes, that is, as if through gushes urging water downwards. "by which the world that then was, being overflowed with water, perished." It perished, not for the entire world, but for the living beings, which indeed represent the whole world.
If indeed the place was deserted of living beings, the world would not even be considered. Furthermore, what is stated, "reserved for fire on the day of judgment of ungodly men," is thus arranged: reserved for the day of judgment and for the day of destruction; for "on the day" is resumed from common sense. However, judgment means condemnation:

But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day. The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering toward us, not willing that any should perish, but that all should come to repentance.
"The Lord is not slack." Having completed the discourse on the End, which will necessarily be through fire, all of which we have explained more fully, it transitions to the production or extension of the time until the world is ended, and says: The Lord is not slack concerning his promise, as some understand slowness. Instead, he is patient, waiting for our salvation, not willing that any should perish, but that all should come to repentance: for certainly to him who is infinite and the sea of essence unconstrained, nothing is extended, but a thousand years are just like a single day with him. Or rather, according to David, there is no multiplication of days: for he says in this way: "A thousand years in your sight, O Lord, are like a day that has just gone by and like a watch in the night" (Ps. 89:4): by watch signifying the briefest span of the night. For the night is divided into four watches: since the Lord came to the holy apostles in the fourth watch. (Matt. 14:25)

But the day of the Lord will come as a thief in the night, in which the heavens will pass away with a great noise, and the elements will melt with fervent heat, and the earth and the works that are in it will be burned up.
The uncertainty of the Lord's coming is signified as a theft, when it is least expected, through the thief and the night: through the night indeed, because of uncertainty; for all things in the night are uncertain: through the thief, because he is not expected; for no one will be robbed who expects a thief, but those who least expect him will be robbed. Therefore, the Lord also says that just as in the days of Noah there were men rejoicing in weddings and drinking, thinking nothing of the future calamity that would overtake them (Matt. 24:38), until the flood overwhelmed them: so too will the coming of the Lord suddenly come upon the wicked.
The word "noise" (᾿Ροιζηδὸν) indeed means sound. However, the sound of this kind is proper to fire in those things that are fed by fire. Note, however, that it has said the earth and what is in it must be burned up, but not men, but only destruction has been said concerning the wicked or their transgressions. For the way of the wicked will perish, but the wicked himself will not.

Therefore, since all these things will be dissolved, what manner of persons ought you to be in holy conduct and godliness, looking for and hastening the coming of the day of God, because of which the heavens will be dissolved, being on fire, and the elements will melt with fervent heat? Nevertheless, we, according to His promise, look for new heavens and a new earth in which righteousness dwells. Therefore, beloved, looking forward to these things, be diligent to be found by Him in peace, without spot and blameless, and consider that the long-suffering of our Lord is salvation.
"According to his promise." For He promised the faithful, saying: "I will come and take you, etc. (Jn. 14:33) "In my Father's house there are many mansions." (Jn. 14:2) Therefore, Paul also says that, when the angel shall sound the trumpet from heaven, and the dead shall rise immortal (1 Thess. 4:15), they themselves will also meet the Lord in glory, signifying immortality by what he said about glory. But if they are immortal or incorruptible, surely they will also be new. If, however, these are new, it is evident that a new creature has been born to be changed along with the establishment of men: corruptible indeed because of the corruptible downfall of men, but incorruptible because of the renewal of men. Consider, moreover, that both the delay of time until the Lord's coming and the long-suffering expectation itself are said to effect our salvation.

Just as our beloved brother Paul, according to the wisdom given to him, has written to you, speaking in almost all his letters about these things: among which are some things hard to understand, which the unlearned and unstable distort, as they do the other Scriptures, to their own destruction.
"Just as our beloved brother Paul," And where did Paul say anything of this sort? In these words when he says: "The goodness of God invites you to repentance." (Rom. 2:4) If the patience of God invites to repentance, then repentance is certainly beneficial for us, and the patience of God is for our benefit and salvation.
However, he says that the things hard to understand are interpreted by the wicked in a perverse way; for this means to be twisted, and to demonstrate the whole matter from one point, as Paul said, "Where sin increased, grace abounded all the more," (Rom. 5:20) they perverted this to mean that we sin more so that we may be forgiven more abundantly.
However, they do this, he says, to their own destruction. Just as those who killed the prophets and apostles are liable to the same judgment, so too are those who distort their words: for those killed them so that those who were being taught salvation by them could not be helped by them; and likewise, these distort the words so that no one may work salvation through them.