The day of the Lord is not to come till the man of sin be revealed. The apostle’s traditions are to be observed.

¹ But we ask you, brothers, concerning the advent of our Lord Jesus Christ and of our gathering to him,

² that you not be readily disturbed or terrified in your minds, by any spirit, or word, or epistle, supposedly sent from us, claiming that the day of the Lord is close by.

³ Let no one deceive you in any way. For this cannot be, unless the apostasy will have arrived first, and the man of sin will have been revealed, the son of perdition,¹²³

1. 2:3The word ‘discessio’ in this verse has long been understood in the Catholic Church to refer to the great apostasy, which occurs during the tribulation. And in as much as the tribulation is divided into two parts, then so also will there be two great apostasies, one during the first part of the tribulation, which is but a dim reflection of that more extensive great apostasy during the second part of the tribulation. The Antichrist, as one particular human person, is of the second part of the tribulation; he is not present in the world today.(Conte)
2. 2:3A revolt: This revolt, or falling off, is generally understood, by the ancient fathers, of a revolt from the Roman empire, which was first to be destroyed, before the coming of Antichrist. It may, perhaps, be understood also of a revolt of many nations from the Catholic Church; which has, in part, happened already, by means of Mahomet, Luther, etc., and it may be supposed, will be more general in the days of the Antichrist.(Challoner)
3. 2:3The man of sin: Here must be meant some particular man, as is evident from the frequent repetition of the Greek article: o`, ‘the’ man of sin, ‘the’ son of perdition, ‘the’ adversary or opposer. It agrees to the wicked and great Antichrist, who will come before the end of the world.(Challoner)

⁴ who is an adversary to, and who is lifted up above, all that is called God or that is worshipped, so much so that he sits in the temple of God, presenting himself as if he were God.¹

1. 2:4In the temple: Either that of Jerusalem which some think he will rebuild; or in some Christian church, which he will pervert to his own worship: as Mahomet has done by the churches of the east.(Challoner)

⁵ Do you not recall that, when I was still with you, I told you these things?

⁶ And now you know what it is that holds him back, so that he may be revealed in his own time.¹

1. 2:6What is it that holds back the Antichrist from being in the present time? It is the holy Eucharist. In the generations preceding the arrival of the Antichrist, the Eucharist and the true Mass will be diminished extensively throughout the world, Christians will become a hated minority, and the world will immerse itself in every kind of sin, and in hatred for all true religion.(Conte)

⁷ For the mystery of iniquity is already at work. And only one now holds back, and will continue to hold back, until he is taken from our midst.¹

1. 2:7The one who holds back the mystery of iniquity, so that it does not result in the actual arrival of the person of the Antichrist, is Christ present in the holy Eucharist. That is why the abomination of desolation, a false Eucharist is associated with the Antichrist. When the abomination replaces the Eucharist, then the Antichrist begins his reign of terror against the Church.(Conte)

⁸ And then that iniquitous one shall be revealed, the one whom the Lord Jesus shall bring to ruin with the spirit of his mouth, and shall destroy at the brightness of his return:¹

1. 2:8As we learn from the Book of Revelation, the Antichrist is never killed, but he is sent alive, body and soul, with the false prophetess, into the destruction of Hellfire: “These two were cast alive into the pool of fire burning with sulphur.” (Rev 19:20). The word ‘interficiet’ does not always refer to death per se.(Conte)

⁹ him whose advent is accompanied by the works of Satan, with every kind of power and signs and false miracles,

¹⁰ and with every seduction of iniquity, toward those who are perishing because they have not accepted the love of truth, so that they may be saved. For this reason, God will send to them works of deception, so that they may believe in lies,¹

1. 2:10God shall send: That is God shall suffer them to be deceived by lying wonders, and false miracles, in punishment of their not entertaining the love of truth.(Challoner)

¹¹ in order that all those who have not believed in the truth, but who have consented to iniquity, may be judged.

¹² Yet we must always give thanks to God for you, brothers, beloved of God, because God has chosen you as first-fruits for salvation, by the sanctification of the Spirit and by faith in the truth.

¹³ He has also called you into truth through our Gospel, unto the acquisition of the glory of our Lord Jesus Christ.

¹⁴ And so, brothers, stand firm, and hold to the traditions that you have learned, whether by word or by our epistle.¹

1. 2:14Traditions: See here that the unwritten traditions are no less to be received than their epistles.(Challoner)

¹⁵ So may our Lord Jesus Christ himself, and God our Father, who has loved us and who has given us an everlasting consolation and good hope in grace,

¹⁶ exhort your hearts and confirm you in every good word and deed.