From: 2 Peter 3:8-14
 But do not ignore this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day.  The Lord is not slow about his promise as some count slowness, but is forbearing toward you, not wishing that any should perish, but that all should reach repentance.  But the day of the Lord will come like a thief, and then the heavens will pass away with a loud noise, and the elements will be dissolved with fire, and the earth and the works that are upon it will be burned up.
Moral Lessons to be Drawn
 Since all these things are thus to be dissolved, what sort of persons ought you to be in lives of holiness and godliness awaiting for and hastening the coming of the day of God, because of which the heavens will be kindled and dissolved, and the elements will melt with fire!  But according to his promise we wait for new heavens and a new earth in which righteousness dwells.
 Therefore, beloved, since you wait for these, be zealous to be found by him without spot or blemish, and at peace.
8. This passage from v. 4 of Psalm 90 was often cited by Jewish rabbis in their calculations about how long the messianic times would last and when the end of the world would be; later on, millenarists would use it as a basis for their farfetched theories about Christ and his saints bearing temporal rule for a thousand years over an earthly kingdom prior to the End. The author of the letter cites the psalm as an authority for the view that time is a function of Creation and has no connection with the eternity of God: the fact that the Parousia has not happened is no reason to deny that it will happen.
9-10. In this passage we are reminded that God, in his great mercy, does not seek our condemnation but, rather, wants all men to be saved (cf. 1 Tim 2:4; Rom 11:22) and shows wonderful patience towards them. The fact that the Parousia has not yet come about is quite compatible with the certainty that it will happen, and happen all of a sudden; therefore, far from being an excuse for making Christian life less demanding, the Parousia is a spur to stay vigilant (the Master himself used the simile of the thief: cf. Mt 24:43 44; Lk 12:39). "Since we know neither the day nor the hour, we should follow the advice of the Lord and watch constantly so that, when the single course of our earthly life is completed (cf. Heb 9:27), we may merit to enter with him into the marriage feast and be numbered among the blessed (cf. Mt 25:31-46) and not, like the wicked and slothful servants (cf. Mt 25: 26), be ordered to depart into the eternal fire (cf. Mt 25:41)" (Vatican II, "Lumen Gentium", 48).
"The earth and the works that are upon it": there are so many variants in the Greek manuscripts that it is almost impossible to reconstruct the original text: but they all convey the idea that the earth will be affected by this universal cataclysm.
11-16. The writer now follows up these considerations with a moral exhortation, based on the conviction that the old world will disappear (v. 12) producing new heavens and a new earth (v. 13), and that men living in the period prior to this cataclysm will not know when it is going to happen (v. 15).
All this should not make Christians afraid; in fact, it should bolster their hope (vv.12-14). God will keep his promise to grant heaven to those who persevere in good; but this hope of future reward should not lead one to neglect temporal affairs: "Far from diminishing our concern to develop the earth, the expectancy of a new earth should spur us on, for it is here that the body of a new human family grows, foreshadowing in some way the age which is to come" (Vatican II, "Gaudium Et Spes", 39).
Hope opens the way to upright conduct (v. 11) of an even higher standard (v. 14). Christians should realize that they have a pressing duty to grow in virtue as long as they live in this world (v. 15): "God may have given us just one more year in which to serve him. Don't think of five, or even two. Just concentrate on this one year that has just started. Give it to God, don't bury it! This is the resolution we ought to make" (St. J. Escriva, "Friends of God", 47).
The practice of virtue leads to holiness and enduring union with God (v. 14; cf. 1 Thess 3:13). "'While we are at home in the body we are away from the Lord' (2 Cor 5:6) and, although we have the first fruits of the Spirit, we groan inwardly (cf. Rom 8:23) in our anxiety to be with Christ (cf. Phil 1:23). The same love urges us to live more for Him who died for us and who rose again (cf. 2 Cor 5:15). We make it our aim, then, to please the Lord in all things (cf. 2 Cor 5:9) and we put on the armor of God that we may be able to stand against the wiles of the devil and resist the evil day (cf. Eph 6: 13)" ("Lumen Gentium", 48).
12. "Waiting for and hastening": these two verbs convey the idea that Christian hope is something dynamic; it is in no way passive. Contrary to a view quite widespread among the Jews of the time, it does not mean that the Parousia will come sooner, the more meritorious men are; what it means is that the more closely united to Christ they are, the nearer they are to his glory. Therefore, it is urgent that all should embrace faith in Christ. We who have this faith pray in the Our Father, "Thy kingdom come." The first Christians made the same petition in their ejaculatory prayer, "Marana tha", "Come, Lord" (1 Cor 16:22; Rev 22:20), referring to the second coming of the Lord.
"The day of God": the usual expression in the New Testament is "the day of the Lord" (1 Cor 1:8; 5:5; 1 Thess 5:2; 2 Thess 2:2; 2 Pet 3: 10); both expressions refer to the point at which Christ will come to judge the living and the dead.
13. "New heavens and a new earth": one of things promised for the End is that creation will be renewed, re-fashioned: the prophets proclaimed this (cf. Is 65:17), and the New Testament speaks of drinking new wine at the heavenly banquet (cf. Mt 14:25), being given a new name (cf. Rev 2:17), singing a new song (cf. Rev 5:9), living in a new Jerusalem (Rev 21:3). All this imagery conveys the idea that the whole universe will be transformed, man included (cf. Rom 8:19-22). "We know neither the moment of the consummation of the earth and of man (cf. Acts 1:7) nor the way the universe will be transformed. The form of this world, distorted by sin, is passing away (cf. 1 Cor 7:31), and we are taught that God is preparing a new dwelling and a new earth in which righteousness dwells (cf. 2 Cor 5:2; 2 Pet 3:13), whose happiness will fill and surpass all the desires of peace arising in the hearts of men" ("Gaudium Et Spes", 39).
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.