18 Grk “the ones who are upsetting you.” The same verb is used in Acts 21:38 to refer to a person who incited a revolt. Paul could be alluding indirectly to the fact that his opponents are inciting the Galatians to rebel against his teaching with regard to circumcision and the law.
19 Grk “would even.”
20 Or “make eunuchs of themselves”; Grk “cut themselves off.” This statement is rhetorical hyperbole on Paul’s part. It does strongly suggest, however, that Paul’s adversaries in this case (“those agitators”) were men. Some interpreters (notably Erasmus and the Reformers) have attempted to soften the meaning to a figurative “separate themselves” (meaning the opponents would withdraw from fellowship) but such an understanding dramatically weakens the rhetorical force of Paul’s argument. Although it has been argued that such an act of emasculation would be unthinkable for Paul, it must be noted that Paul’s statement is one of biting sarcasm, obviously not meant to be taken literally. See further G. Stählin, 3:853–55.

In other versions

I wish those who unsettle you would emasculate themselves!

As for those agitators, I wish they would go the whole way and emasculate themselves!

I wish those who are disturbing you might also let themselves be mutilated!

I just wish that those troublemakers who want to mutilate you by circumcision would mutilate themselves.

I wish that the ones who are disturbing you would also castrate themselves!

I would they were even cut off which trouble you.

Public Domain