Now Paul begins to touch upon another cornerstone of Jewish confidence and pride, namely their circumcision.  Being one of them, he well knew that the Jew was sure his circumcision, and participation in the covenant made with Abraham, gave him a leg up on his fellow men where God was concerned.  The apostle will begin here, and say much hereafter, to dispel this vain notion.  Like Christ and John the Baptist before him, he is concerned to dismantle every hope that any person may have for acceptance with God apart from the blood and righteousness of the Lord Jesus Christ.

Thus, he tells them that hypothetically their circumcision may be profitable to them, but only if they keep the rest of the law.  But he has just reminded them that their own scriptures prove that they did not keep the law, but on the contrary even gave opportunity for the enemy to blaspheme the name of God through their rebellion.  Therefore, the point is moot.  Circumcision truly was an act of obedience, but what good was it to have a mark in the flesh if the rest of the life was out of order?  In the law and the prophets we often find God urging the people of Israel to circumcise their hearts, indicating thereby that circumcising the flesh was of no value while the heart remained corrupt and unrenewed.  He tells them, then, that if they are breakers of the law, their circumcision is made uncircumcision.  I do not think he means to discount the value of obeying God, Who had commanded the Hebrew parents to circumcise their sons.  Rather, he is reminding them of what they should have learned from the prophets, that God was not impressed by the mark of the covenant in their flesh.  If they were living in rebellion to His commandments, they may as well not even bother being circumcised, for it made them no better off.  They certainly were not going to be allowed a place in heavenly glory simply because they were circumcised.