v1 – It seems strange that you would ever need to tell anyone not to submit to slavery. Surely no one would ever knowingly submit to slavery, but evidently Paul thought there was a risk that the Galatians would submit. I can only assume that’s because they didn’t recognise that what they were submitting to would enslave them.
As Paul has explained earlier in the letter, and as all of us here know, we’re saved by faith, not works. If you try to earn your salvation by works of the law, no matter how hard you work, you won’t get any reward. The law will enslave you.
Christ didn’t set us free for slavery. He set us free for freedom. And note the word “therefore” in v1. For freedom Christ has set us free, therefore do not submit to a yoke of slavery. We must not submit to slavery because of what Christ set us free for. He set us free for freedom, so if we submit to slavery, it will contradict what he set us free for – what he saved us for – we must hold onto freedom for the sake of the gospel.
I think it’s important to understand that the reason we resist the yoke is for the sake of the gospel, because otherwise we might take this out of context and use it as an excuse to do what we want. In church life, and in life in general, there are going to be things we want to do that conflict with what other people want. This verse isn’t telling us to stand firm and demand that we get our own way.
The point is we’re set free from trying to work to make ourselves pleasing to God. Of course, in response to the love God’s shown us, we will want to please him, but the way to do that is not to go back to the slavery that he set us free from. God won’t be pleased if we reject his grace and try to earn his favour instead; he will be pleased if we live in a way that magnifies his grace.
v2 – “if you accept circumcision, Christ will be of no advantage to you” – but in Acts 16 Paul circumcised Timothy, so it’s not really the physical circumcision that’s the issue, but the participation in this false religion in which your standing before God really depends on your performance, rather than Christ’s performance.
Paul is talking to people who wanted and expected Christ to be of some advantage to them, but if they accepted circumcision, he wouldn’t be. If you try to add some of your own performance to Christ for your justification, you’ll lose Christ.