When Paul urges the Judaizers who trouble the Galatian churches to “mutilate themselves” (Galatians 5:12), it seems like a crude joke. They like cutting foreskins; might as well go all the way to cut off the whole thing.
But it’s not just a vulgar insult. As many commentators have noted, Paul virtually equates circumcision with castration, which, far from being a mark of inclusion in Israel is a reason for exclusion (Deuteronomy 23:1). But a student, Grace Langness, points out that there may be something else happening. Circumcision is literally a removal; it is a privation. To take pride in circumcision is to take pride in an absence. This is the irony of the Judaizers position: They treat circumcision as a sign of power, when in fact it is a sign of human impotence, the impotence of the flesh. Whey they glory is circumcision, they glory in what is not there; they glory in nothing.