Paul today continues on his point that law seriously limits liberty in vv.7-12.
You were running well; who prevented you from obeying the truth? This persuasion does not come from the one who calls you! A little yeast makes the whole batch of dough rise! I am confident in the Lord that you will accept no other view. But the one who is confusing you will pay the penalty, whoever he may be. Now, brothers and sisters, if I am still preaching circumcision, why am I still being persecuted? In that case the offense of the cross has been removed. I wish those agitators would go so far as to castrate themselves!
Is this the strongest thing that Paul ever wrote, down in v.12? Maybe, maybe not, but it is certainly strong, isn’t it?
His pastoral heart is on show first in v.7 and we can imagine him lamenting over the Galatians, you were running well; who prevented you from obeying the truth? As he goes on to say, this is not from God (v.8) and it only takes a little law to limit liberty (v.9). Paul goes on to say that he still believes that the Galatians can tell truth from error (v.10a), and that the ringleader of this Judaizing, false teaching will pay the penalty.
To answer accusations he was also preaching that circumcision was necessary for salvation, he writes
…that if I am still preaching circumcision, why am I still being persecuted? In that case the offense of the cross has been removed.
Very simply, Paul was not preaching circumcision (or any other kind of works-based salvation) and was actively being persecuted for preaching the cross of Christ alone (1 Corinthians 1.23). He is so obviously (and understandably) worked up about this accusation that the tone changes and he says that he wishes that those spreading such slanderous untruths would go so far as to castrate themselves!
Pagan priests in the region at the time would actually do this to show piety and devotion, so, Paul’s thinking in his frustration and annoyance is along the lines of “Well, if you’re teaching that, why not just go ahead and do the full job?”.
Reading this with our modern and often delicate sensibilities can leave us feeling shocked: did Paul really just say he wishes they would castrate themselves? How barbaric…But, context is wonderful and the Galatians would have understood instantly the point he is making.
If they were dabbling in a little law, they might as well trade all the liberty of a life lived in the grace of God and go all out pagan.
If they were considering adding a little work here or there to boost their chances of justification, then why not go all-in?
A little circumcision, why not a lot of castration?
You get the picture.
He is being sarcastic,
he is writing with hyperbole,
but the point he is making could not be any more serious.
As he said in a somewhat more mellow manner in v.9, a little law limits liberty. To dabble in works-based righteousness was exactly the same as doing the most severe thing possible. His point is clear: stay well away from those who want you to trade your liberty for law, because even a little law will severely limit your liberty.