2 Thessalonians 2:1-4
Verses 1 & 2
The Thessalonian Christians were 'shaken', believing that the coming of the Lord Jesus Christ and 'our gathering together with Him', described in Paul's first letter to them, had already occurred, leaving them behind. (Of course, they should have been encouraged by the fact that Paul was still there, too!)
Some believe that the 'day of the Lord' spoken of in verse 2 does not refer to the Rapture, but rather to Christ's Second Coming. However, they overlook two important things. First, that verse 1 treats the both events as one event, and second, that in his first letter, Paul used the phrase 'day of the Lord' to refer to the Rapture. The nervous response of the Thessalonian Christians also gives credence to the view that it is the Rapture that Paul has in mind in this passage, for they would not have minded missing that 'day' if it only referred to the day of the Lord's wrath! So it is the Rapture that they were afraid they had missed!
In this second letter, Paul tries to alleviate their fears by revealing two events that will precede Christ's coming, warning them of His appearing. He tells them that the Rapture 'will not come unless' these two events occur 'first'! He prefaces this by warning them to beware of those who would seek to 'deceive' them by teaching them otherwise. Those who teach the imminent pre-tribulation Rapture as a separate event from the second coming of Christ are spreading a doctrine that is contrary to what Paul is teaching here, and may very well be the ones Paul has in mind!
Verses 3 & 4
The first event Paul instructs the Thessalonian Christians to look for that will signal the coming Rapture is the apostasy, which Paul says must 'come first'. There has been much written about some denominations falling away, or apostasizing, from doctrinal beliefs based solely on the Bible. This has resulted in the infiltration of many worldly customs and beliefs such as the rejection of the Biblical Creation account, the idea that all religions are basically the same, the acceptance of homosexual unions and the rejection of the Bible as absolute Truth. This kind of doctrinal apostasy has been cited as evidence of a present state of apostasy in some parts of the Christian Church.
However, in view of Matthew 24, the apostasy Paul has in mind would seem to be linked to the persecution of the Church causing many to fall away and betray even their own family members. This type of apostasy will immediately precede the Lord's coming.
Along with, and perhaps the reason for, this apostasy is the second event ... the revelation of the 'man of lawlessness'. His appearance is prophesied in Daniel as well as in Revelation, and he will exalt himself to heights none have previously dared to scale, and will even enter the temple of God and proclaim himself to be God! Now that will be an event difficult to miss!
So remember, Paul said that Jesus will not be coming to gather us to Himself unless these two events take place first! Do not be deceived into thinking otherwise!