At a first glance, 2 Thessalonians 3 seems to just be a chapter Paul wrote to encourage the church to stay busy. But a closer look reveals what may be the foundation of what we know as “excommunication” from whatever denomination that practices it comes from.
We start off with a prayer request from Paul: That the word of God spread and prosper, that the church be spared from evil, and that the church be strengthened to do what’s right:
1 Finally, brothers, pray for us, that the word of the Lord may speed ahead and be honored, as happened among you,
2 and that we may be delivered from wicked and evil men. For not all have faith.
3 But the Lord is faithful. He will establish you and guard you against the evil one.
4 And we have confidence in the Lord about you, that you are doing and will do the things that we command.
5 May the Lord direct your hearts to the love of God and to the steadfastness of Christ.
Then, boom, Paul just comes out and says the thing:
6 Now we command you, brothers, in the name of our Lord Jesus Christ, that you keep away from any brother who is walking in idleness and not in accord with the tradition that you received from us.
Now, this being the ESV (English Standard version), “walking in idleness” sounds like a very gentle way of saying “lazy” or “unproductive”. In other versions, it’s not so gentle:
(NAS - New American Standard)
6 Now we command you, brethren, in the name of our Lord Jesus Christ, that you keep away from every brother who leads an unruly life and not according to the tradition which you received from us.
(KJV - King James Version)
6 Now we command you, brethren, in the name of our Lord Jesus Christ, that ye withdraw yourselves from every brother that walketh disorderly, and not after the tradition which he received of us.
(LEB - Lexham English Bible)
6 But we command you, brothers, in the name of our Lord Jesus Christ, [that] you keep away from every brother who lives irresponsibly and not according to the tradition that they received from us.
We see the use of “unruly”, “disorderly”, irresponsibly"–all of which sound way more aggressive. But the point is that Paul is calling out the people who have heard the gospel, claim to be a Christian, but do not either: work in the ways a Christian should, lead a Christian life, or are just lazy, or maybe even all three. We get some more context in the following verses (ESV):
7 For you yourselves know how you ought to imitate us, because we were not idle when we were with you,
8 nor did we eat anyone’s bread without paying for it, but with toil and labor we worked night and day, that we might not be a burden to any of you.
9 It was not because we do not have that right, but to give you in ourselves an example to imitate.
10 For even when we were with you, we would give you this command: If anyone is not willing to work, let him not eat.
11 For we hear that some among you walk in idleness, not busy at work, but busybodies.
12 Now such persons we command and encourage in the Lord Jesus Christ to do their work quietly and to earn their own living.
Paul is saying that people shouldn’t use their positions as “Christians” as an excuse to not work, or perpetuate slothfullness. At the same time, we shouldn’t make an exorbitant show of “how busy we are”, ever the busybody and unable to work in the things we should. Another perspective on this same chapter, from Matthew Henry in his work, ‘Matthew Henry Commentary on the Whole Bible (Concise)’:
It is a great error and abuse of religion, to make it a cloak for idleness or any other sin.
Now, in no way is Paul asking the church to condemn those who fall under this category, and we see it explained here in the following verses:
13 As for you, brothers, do not grow weary in doing good.
14 If anyone does not obey what we say in this letter, take note of that person, and have nothing to do with him, that he may be ashamed.
15 Do not regard him as an enemy, but warn him as a brother.
We are not to seek ways to directly shame them, but by lack of association they will feel ashamed of what they are doing. Not only are we to not go on the offensive with them, but also not regard them as an enemy. They are your bothers/sisters after all! There was a reason they found the Gospel to resonate with them and they have come a lot further than many others who flat out reject the word of God. We are to instead warn them as a brother.
Now, the family dynamic is hugely different for many people. Some might be tempted to follow the example of what you grew up with in your own family, with your siblings. Heated arguents, the silent treatment, even physical altercations included–we are all at least aware of “sibling rivalry”. But the type of brother Paul is talking about isn’t a sibling brother you were born with. He’s talking about being brothers in Christ. That means you have a godly love for each other. You want to help your brothers to genuinely seek God. You want your brothers to find the joy in serving God. Because of this, you should warn them of falling away from path God wants us to follow. You should warn them of the ways they act in contrast to the Gospel. And as a true brother in Christ, you will do this with love, not hate.
16 Now may the Lord of peace himself give you peace at all times in every way. The Lord be with you all.
17 I, Paul, write this greeting with my own hand. This is the sign of genuineness in every letter of mine; it is the way I write.
18 The grace of our Lord Jesus Christ be with you all.
He signs off here. Verse 16 could be interpreted as just the way he says goodbye, but I believe he actually means it, in fact he prays it. That despite the obvious (possibly heated) discourse that following his instructions will cause, he urges the Lord to maintain our peace with one another–to recognize the love we have for each other as followers of Jesus. And to govern ourselves through that godly love. Because of this I view excommunication as a manmade construct, extreme in measure, that misses the point of this passage.
By following God first, before our own selfish and lazy desires, we strengthen ourselves. And we should seek to help each other do this as well. This is how I’ve come to interpret this chapter.
Edit: Conclusion about excommunication