How does one go about interpreting such a difficult passage?
I suggest that the best way is to look at context, first in this chapter, secondly in the whole of 1 and 2 Thessalonians, and thirdly in other NT passages that appear to touch on the same topic.
Rather than quote the Greek text, I’ll make a literal rendering of the two verses:
And you-all know what is holding down (the man of lawlessness) until he is uncovered in his own time. You see, the secret of lawlessness is already at work. It is just that there is an agent holding him down now (and he/it will continue to do so) until (that agent) is taken away.
The initial ”and” links to the previous verse where Paul is reminding them that he has already told them about the events of the last times before the return of Jesus. We cannot know what Paul told them, but the closest we can get is to look at what he just reminded them about in the previous verses. The topic is introduced in v. 1, namely ”the coming of our Lord Jesus Christ and our being gathered to him.” Paul covered the same topic in 1 Thess 4:13-17, where in v. 17 we read ”we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air.”
Now, in 2:2 Paul is telling his audience not to be alarmed by rumours that the ”coming of the Lord and our gathering to him”, or the ”day of the Lord” as he calls it here, has already taken place (and therefore they were left behind). It doesn’t matter whether such rumours or false teaching have come through a ”spirit” (meaning a prophecy), or a word (probably a word of knowledge), or a letter purported to be written by ”us” (Paul or other apostles).
In 2:3 he continues to tell them that they should not be deceived to believe such rumours/teaching. Why? Because something has not yet happened, namely the rebellion/apostasy and the uncovering/revealing of the man of lawlessness. This topic is similar to 1 John 2:18 ”you all have heard that antichrist shall come.” Not only is he coming, but ”even now is already in the world.” It is reasonable to equate the man of lawlessness with antichrist.
In 2:4 Paul explains how the activities of this evil person will become more and more rebellious against God and end in him exalting himself to be God. This is a process from the initial uncovering to the final height of rebellion followed by judgment, a process that covers many chapters in Revelation, although the focus there is on judgment.
In 2:5 there is a break, and in 2:6 Paul returns to the topic of verse 3, namely that something needs to happen before the coming of Jesus (in the air) and the gathering of the believers with him. That this man of lawlessness is to be revealed does not mean that his evil acts have reached the end point. It is a process that has already started, although in a hidden and secret way as verse 7 tells us. Satan and this man of lawlessness that he controls love to conceal their wickedness under an enticing cloak of light. But at a time set by God his wickedness is to be revealed. It appears that this revealing will be immediately or soon followed by the ”gathering up”, which again will open the door for an increase of wickedness.
There is little doubt that ”what is holding him down” in v. 6 refers to the same entity as ”the agent who is holding him down” in v. 7. The word ”hold down” can also mean ”restrain, suppress” like when you hold down a violent man or hold on to a wild dog in a leash. The dog may be growling and snarling, but until it is released or unleashed, it cannot fully do what it wants to do. The question is what is this entity. A good commentary will list the various suggested options, but most of them are unlikely to be correct. Some have suggested that it might refer to the Holy Spirit. I don’t think this is correct. Morris says about this suggestion:
It seems definite enough to exclude some suggestions as to the identity of the restrainer, for example, that which views him as the Holy Spirit (so the Scofield Reference Bible). While it would be easy to think of the Spirit as restraining the forces of evil, it is impossible to envisage him as being “taken out of the way.” Such an idea does not appear in Scripture.
If we look again at the main topic from verse 1, there is an entity that will be ”taken out of the way”, namely the believers which is also described as ”the body of Christ”. It seems to me to be the best solution to an enigmatic passage. The body of Christ has a restraining effect on the evil in this world, both by actions and prayers, and only when that Body is removed does the antichrist have no opposition left here on earth. Or said differently, God has allowed him to be unleashed.
As with most eschatological concepts, there is not likely to be consensus or agreement. It is just that I wanted to suggest something that I have not seen very often in commentaries, but an option that in my view fits the context of the chapter.