“Rebellion” is the Greek apostasia, “apostasy, abandonment, revolt, rebellion.” Literally, the Greek has “the rebellion.” The presence of the article suggests Paul is not talking about just any rebellion or apostasy, but something well known as a result of the teaching of Paul and his missionary team.
As explained by Thomas in the previous footnote, the words “must come first” refer not to the day of the Lord, but to the revealing of the man of lawlessness. Typically, the popular view takes this to mean there must first be a worldwide rebellion before the judgment part of the day of the Lord can even begin. For instance, Charles Ryrie writes:
… It is the apostasy which will come before the day of the Lord. Apostasia, translated apostasy, does not mean merely disbelieving but rather an aggressive and positive revolt (Acts 21:21; Heb. 3:12). Paul himself later wrote in detail concerning the details of this great departure from the faith in I Timothy 4:1-3 and II Timothy 3:1-5; 4:3-4. In these passages he says that this defection would occur in the last days. It is as though the infidelity of those who profess to be religious will prepare the way and perhaps even furnish the occasion for the final display of revolting against God in the person of the Man of sin. But the day of the Lord will not be present until this great apostasy sweeps the earth.44
So also, in The Bible Knowledge Commentary, Thomas Constable writes:
This is a revolt, a departure, an abandoning of a position once held. This rebellion, which will take place within the professing church, will be a departure from the truth that God has revealed in His Word. True, apostasy has characterized the church almost from its inception, but Paul referred to a specific distinguishable apostasy that will come in the future (cf. 1 Tim. 4:1-3; 2 Tim. 3:1-5; 4:3-4; James 5:1-8; 2 Peter 2; 3:3-6; Jude). He had already told his readers about it (2 Thes. 2:5).45
The apostasy or rebellion clearly refers to a special departure and rebellion against the true God. This will become a worldwide movement and will provide the seed bed for the great system of revolt which will be headed up in the person of the Beast who will be the very personification of Satan himself. As just illustrated, some apply this to the period just before the day of the Lord, i.e., the last days of the church. Others, as Robert L. Thomas (cited earlier), would apply this to the day of the Lord itself which I have come to believe is a better understanding of this passage. Obviously, a growing worldwide departure has been going on for centuries and the apostle even speaks of this in his day (“for the hidden power of lawlessness is already at work” [vs. 7]). In verse 3, however, I believe Paul has in mind the worldwide revolt that occurs in the beginning of the day of the Lord and that opens the way for the system of the man of lawlessness. This fits consistently with the concept of the imminency of both the coming of Christ for the church and that of beginning of the day of the Lord.
*Excerpted from the article 4. Correction Concerning the Day of the Lord—Part 1 (2 Thes. 2:1-5) at Bible.org
Some, such as Bill Salus, have said that the “rebellion” described in 2 Thessalonians 2 is the war of Ezekiel 38 and Psalm 83. I agree with Dr. Reagan of Lamb and Lion Ministries, who proves biblically that Ps. 83 is not a prophecy but rather a prayer of lament, and as such, cannot be the referent of “the rebellion” from 2 Thess. 2 . Likewise, Dr. Mark Hitchcock and Thomas Ice hold this position.
However, the War of Gog and Magog will set the stage for a great deception to which Mr. Keathley refers. We must be sure to interpret 2 Thess. 2 as indicating a vigorous or sudden and intent “falling away” from the Christian faith. The foundations of this apostasy had begun even in Paul’s day with false doctrines and attacks on Christ, which Paul called the mystery of iniquity (2 Thess. 2:7). Within the last 200 years, the spirit of this apostasy has infiltrated protestant evangelicalism through the desire to pander toward Darwinism, anti-biblical ecumenism at the hand of pluralism and esoteric study. But, at a certain time in the future, there will be a culmination of all cunningly devised fables and ancient myths, producing THE “Apostasia.”