“Let no man deceiue you by any meanes, for that day shall not come, except there come a falling away first, and that man of sinne bee reuealed, the sonne of perdition,”
1611 King James Version (KJV)
2:3 Unless the falling away - From the pure faith of the gospel, come first. This began even in the apostolic age. But the man of sin, the son of perdition - Eminently so called, is not come yet. However, in many respects, the Pope has an indisputable claim to those titles. He is, in an emphatical sense, the man of sin, as he increases all manner of sin above measure. And he is, too, properly styled, the son of perdition, as he has caused the death of numberless multitudes, both of his opposers and followers, destroyed innumerable souls, and will himself perish everlastingly. He it is that opposeth himself to the emperor, once his rightful sovereign; and that exalteth himself above all that is called God, or that is worshipped - Commanding angels, and putting kings under his feet, both of whom are called gods in scripture; claiming the highest power, the highest honour; suffering himself, not once only, to be styled God or vice - god. Indeed no less is implied in his ordinary title, Most Holy Lord, or, Most Holy Father. So that he sitteth - Enthroned. In the temple of God - Mentioned #Rev 11:1|. Declaring himself that he is God - Claiming the prerogatives which belong to God alone.
2Th 2:3 Except there come a falling away first. An apostasy must precede the Coming. That is, there shall be a general falling away from the purity of the faith. No apostasy of magnitude occurred in the history of the church for centuries, which could answer to Paul's description, but the gradual declension, corruption, and departure from the ancient faith, which was fully developed a few hundred years later, has always been spoken of by Protestant church historians as "The Apostasy". There is no good reason for doubting that it is to the apostle refers. And that man of sin be revealed. He shall be revealed then in connection with the apostasy. The son of perdition. This expression occurs once elsewhere, and is there applied to Judas, an apostate (Joh 17:12). Here it evidently has a similar application. Some power, once Christian, falls away and becomes opposed to Christ.