Paul’s phrase in context
Paul used this phrase while correcting frightened Christians in Thessalonica. Some had been unsettled by claims that the day of Christ had already arrived. Paul told them that a great falling away and the revealing of “that man of sin” would come first (2 Thessalonians 2:3-4).
Iniquity means lawlessness or rebellion against God. The word “mystery” does not mean a puzzle nobody can understand. In the New Testament, it often describes something once hidden that God has now made known. Paul is saying that a dark, organised rebellion was already at work beneath the surface, even before its final expression became visible (2 Thessalonians 2:7).
For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.
Already working, not yet fully revealed
This mystery was active in Paul’s own day. It appears wherever people resist God’s truth, exalt human authority in God’s place, or use spiritual-sounding claims to lead others away from Christ. Paul particularly connects it with deception, because those who reject truth can become vulnerable to lies that look convincing (2 Thessalonians 2:9-10).
That doesn’t mean every sin, government, or difficult event is the final fulfilment of Paul’s words. Christians have sometimes rushed to identify a particular person as the man of sin. Paul’s point was less about satisfying curiosity and more about helping believers remain steady, love the truth, and refuse deception (2 Thessalonians 2:3-4; 2 Thessalonians 2:10).
Who or what restrains it?
Paul says that something, or someone, was restraining this lawless power until the right time (2 Thessalonians 2:6-7). He does not identify the restrainer clearly in this letter, perhaps because the Thessalonian believers already knew what he meant from earlier teaching.
Faithful Christians have understood the restrainer in different ways. Some see God’s Spirit at work through the church, others see civil order or an angelic power, and others take the wording more broadly as God’s sovereign restraint. The passage leaves room for humility here. What is clear is that evil only proceeds as far as God permits, and only for a time.
Christ has the final word
The mystery of iniquity can sound alarming, especially when evil and confusion seem close at hand. But Paul does not end with fear. The lawless one will not win a long contest against Jesus. Christ will overthrow him by the brightness of his coming (2 Thessalonians 2:8).
So the practical response is not panic or speculation. Hold on to the gospel, test claims by Scripture, and keep loving what is true. Paul encouraged these believers to stand fast in the teaching they had received, and he prayed that God would strengthen them in every good word and work (2 Thessalonians 2:15-17). The mystery of iniquity is real, but Christ’s victory is more certain.
And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: