The Man of Sin is none other than the coming Antichrist. Definitely NOT the pope or the papacy. The Man of Sin, the Son of Perdition, the Beast, that Wicked One, will literally sit in the literal temple in Jerusalem in the future and claim that he is God. This is all the more reason why people today should obey the Gospel and be saved.
2 THESSALONIANS 2
APOSTASY TO BE FOLLOWED BY THE REVELATION OF THE ANTICHRIST
3 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that Man of Sin be revealed, the Son of Perdition;
THE ANTICHRIST WILL CLAIM TO BE GOD WITHIN THE TEMPLE AT JERUSALEM
4 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
PAUL TAUGHT THIS TRUTH TO THE CHURCHES
5 Remember ye not, that, when I was yet with you, I told you these things?
THE HOLY SPIRIT IS PRESENTLY RESTRAINING SATAN AND THE ANTICHRIST
6 And now ye know what withholdeth [RESTRAINS] that he might be revealed in his time. [Note: "in his time" means a future 3 1/2 year period when the world is under the control of the Antichrist]
THE HOLY SPIRIT WILL BE TAKEN OUT OF THE WAY BEFORE THE COMING OF THE ANTICHRIST
7 For the mystery of iniquity doth already work: only He who now letteth will let [THE RESTRAINER WILL RESTRAIN], until He be taken out of the way. [Note: The Holy Spirit (and the Church indwelt by the Spirit) will be taken to Heaven]
THE LORD WILL DESTROY THE ANTICHRIST AT HIS SECOND COMING
8 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: [Note: This will be at the battle of Armageddon]
SATAN CONTROLS AND POSSIBLY POSSESSES THE ANTICHRIST
9 Even him, whose coming is after the working of Satan with all power and signs and lying wonders, [Note: Both the Beast and the False Prophet will be extraordinary miracle workers]
SATANIC MIRACLES WILL DECEIVE THE UNBELIEVING WORLD
10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. [Note: Those who reject Gospel Truth and Bible Truth do not love the truth, therefore will not be saved]
GOD WILL SEND STRONG DELUSION ON EARTH
11 And for this cause God shall send them strong delusion, that they should believe a lie: [Note: The Antichrist will delude the world into thinking that he is the true Christ and God]
SUBMISSION TO THE ANTICHRIST WILL RESULT IN DAMNATION
12 That they all might be damned who believed not the truth, but had pleasure in unrighteousness. [Note: Acceptance of the Mark of the Beast will damn those who take it]
Revelation 11,12, & 13 are all related and reveal what happens during the future reign of the Antichrist. The temple being measured will be a literal temple in Jerusalem, which will be destroyed (through a great earthquake) before the Second Coming of Christ.