Let no one deceive you in any way. For it will not be, unless the departure comes first, and the man of sin is revealed, the son of destruction,
The falling away, as sad as it is, has reference to many Christians leaving God, their faith, and Christianity altogether. Obviously, the subject of apostasy is the central theme in this and the next several verses. Paul is telling the Thessalonians the return of Christ cannot come until this event takes place. It is most likely Jesus equally has reference to this falling away when He says; "And many false prophets shall rise, and shall deceive many" (Matthew 24:11). Paul, in writing to Timothy, speaks of the falling away: "Now the spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils" (1 Timothy 4:1). In Paul’s second letter to Timothy, he says, "For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; and they shall turn away their ears from the truth, and shall be turned unto fables" (2 Timothy 4:3-4).