"The day of the Lord": below it is called the day of God (2 Pet 3:12). Therefore the day of the Lord and the day of God are one and the same name. It is so called in both the Old and New Testaments (cf. Joel 1:15; Isa 2:12; Ezek 13:5; Jas 5:7). In the New Testament there is also mention of the day of Christ (2 Thess 2:2), and the day of the Lord Jesus (2 Cor 1:14).
This day will come as a thief comes at night. Christ Himself used this image when He spoke of the coming of that day (Mt 24:43; Lk 12:39). The Apostle Paul used it also (1 Thess 5:2), as did the Apostle John in the Apocalypse (Rev 3:3; Rev 16:15).
A thief usually comes at night, when people usually sleep, so that no one may notice him. Therefore he usually comes unexpectedly and suddenly for people. For this reason fear and alarm accompany him. For those who do not spiritually slumber, but watch, this day will of course be fearful and overwhelming. They are attentive to their spiritual state and understand the signs of the times (Mt 16:3). Yet for them it will also be joyful (Lk 21:28 and note). It will not be wholly unexpected, for it has been foretold (cf. 1 Thess 4:16).
With this image there is also a secondary thought. Those sunk in sinful sleep and carelessness will lose, at this decisive event, everything they have acquired and possessed. For the thief will snatch it all away and destroy it (Mt 13:12; Jn 10:10).
"At night": the word does not mean that the event will occur at night, that is, the coming of Christ and the judgment. This will be a day. The word "at night" refers to the thief and is joined with that word, not with the word "will come."
"The heavens will pass away with a noise": the word "with a noise" is used when one speaks of a strong wind or storm, a thundering chariot, a roaring waterfall, or a sea surging terribly. It is used of a roaring beast, a raging fire, a collapsing building, and of everything that acts with extraordinary and immeasurable noise.
"Will pass away": they will come to an end. The same word is used by the Lord Himself in the same sense (Mt 24:35; cf. Isa 34:4; Rev 20:11).
"The elements, being burned up, will be dissolved": the elements are the simplest fundamental component parts of nature. It goes without saying that the elements are not understood in the sense of modern chemistry. They are understood in the sense of the ancient conceptions, according to which, as is well known, there were four basic elements: fire, water, air, and earth (cf. Wis 7:17; Wis 19:17). Earth is understood not as the earthly globe in general, but as one of the component elements of that globe.
"Being burned up": the destruction will come chiefly through the action of fire (cf. 2 Pet 3:7).
"Will be dissolved": but not annihilated. There will follow the destruction of the old heaven and the old earth, which will be renewed by transformation. When the almighty sustaining power of God, which supports the universe as the soul supports the body, is withdrawn from it, it will be like a dead corpse. But when restored, it will live again and appear in a new form.
"The earth and the works": the earth and everything on it, nature and human art, trees, plants, minerals, animals, cities and houses, tools, institutions, and so forth (cf. Hab 2:13), will all be terribly destroyed by the action of fire.
"Observe: the Apostle said, the earth and the works on it will be burned up, and not men. Therefore he speaks only of the destruction of the impious and their impious works. For the way of the impious will perish (Ps 1:6), but not the impious man himself together with it" (Theophylact).