Paul writes with a direct command: do not be quickly shaken. The Thessalonians had received reports—perhaps a spirit, a spoken word, or even a letter claiming to be from Paul—that the day of the Lord had already arrived. Paul does not address their anxiety with vague comfort. He names the source of their confusion and tells them to stop being troubled. The pressure is not merely emotional; it is doctrinal. Something specific must happen before that day comes.
Paul gives two events that must precede the day of the Lord. First, a falling away. Second, the revealing of the man of lawlessness, whom he also calls the son of perdition. This figure opposes and exalts himself against everything called God or worshipped. He even seats himself in the temple of God, proclaiming himself to be God. Paul does not explain the temple or the timing in detail. He simply states that this man will be revealed, and his actions are unmistakable.
The Thessalonians already knew these things. Paul reminds them that he taught this while he was with them. The chapter does not fill in what else he said. It only records that they had been told. Paul then introduces a restraining force. The Thessalonians know what it is. Paul writes, “You know that which restraineth, to the end that he may be revealed in his own season.” The restraint is active now. It will continue until it is taken out of the way. Only then will the lawless one appear.
Paul calls the present situation a mystery of lawlessness. That mystery is already at work. But something—or someone—holds it back. The chapter does not name the restrainer. It simply says the restrainer exists, and that its removal will allow the lawless one to be revealed. Paul does not speculate. He states the fact and moves on.
When the lawless one does come, his arrival will be accompanied by the working of Satan. Paul lists the tools: all power, signs, lying wonders, and every deceit of unrighteousness. These are not neutral displays. They are designed for those who are perishing. The chapter gives the reason: they did not receive the love of the truth so that they might be saved. The deception targets people who already rejected the truth.
Then Paul makes a severe statement. God sends them a working of error so that they believe the lie. The purpose is judgment. Those who did not believe the truth but took pleasure in unrighteousness will be judged. The chapter does not soften this. It does not explain how God sends error. It simply says it happens, and the result is that all who refused the truth are condemned.
Paul then turns sharply. He gives thanks for the Thessalonians. God chose them from the beginning for salvation through sanctification by the Spirit and belief in the truth. They were called through Paul’s gospel to obtain the glory of the Lord Jesus Christ. The contrast is deliberate. The perishing refused the truth and received deception. The Thessalonians believed the truth and received salvation. Both outcomes rest on the same gospel call.
Paul ends with a command and a prayer. Stand fast. Hold the traditions they were taught, whether by Paul’s spoken word or by his letter. Then he prays that the Lord Jesus Christ and God the Father—who loved them and gave them eternal comfort and good hope through grace—would comfort their hearts and establish them in every good work and word. The chapter does not end with a warning. It ends with a foundation. The Thessalonians have been taught. They know what restrains. They know what will come. They are to hold what they have been given and trust the one who called them.