2Thessalonians 2:3-4 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; Who opposes and exalts himself above all that is called God, or that is worshipped; so that he as God sits in the temple of God, showing himself that he is God.
‘Let no man deceive you by any means.’ The purpose of the epistle was to calm believers and assure them that the day of Christ (the Lord, as in the texts) had not yet come; that apostasy and the Antichrist must first come; that the rapture must take place even before these two events (2:3-8); that he did not write any such letter as used by the false teachers who were disturbing them; and that he had not changed his doctrine since seeing them and writing the first epistle to them.
‘For that day shall not come, except there come a falling away first, and that man of sin be revealed.’ Two events precede the Day of the Lord:  The falling away [Greek: apostasia] defection, revolt, apostasy. Used only here and in Acts 21:21, but the same as apostasy, divorce, in Matthew 5:31; 19:7 and Mark 10:4. The Greek here has the definite article, “the apostasy,” referring to the great apostasy during the tribulation days between the rapture and the second coming of Christ (Matt. 24:4-31; Rev. 6:1-19:21). At the rapture of all dead and living in Christ in a moment (1Cor. 15:23, 51-58; 1Thess. 4:13-18), not one soul will be left on earth who is a Christian. Multitudes will soon be saved afterwards through an awakening (Acts 2:16-21; Rev. 6:9-11; 7:1-21; 12:17). The rest will become so hardened as to seek to destroy these being saved in those days (Rev. 9:20-21; 16:2, 9-11).
To be continued…