God’s impartiality in judgment is seen now even as He deals with the Jews. For even if they’re circumcised and have the oracles of God (Vv.17-21) but don’t obey its commands to not steal, commit adultery, and thus abhor idols, then they too are judged as lawbreakers who dishonor God. In fact this disobedience is the cause of God’s name being blasphemed among the Gentiles (Vv.21-24).
Moreover, true circumcision is not an outward physical reality but an inwardly motivated act to do Gods’ will. That is, if the circumcised man is a lawbreaker, circumcision is of no use:
“25 For indeed circumcision is of value if you practice the Law; but if you are a transgressor of the Law, your circumcision has become uncircumcision. 26 So if the uncircumcised man keeps the requirements of the Law, will not his uncircumcision be regarded as circumcision? 27 And he who is physically uncircumcised, if he keeps the Law, will he not judge you who though having the letter of the Law and circumcision are a transgressor of the Law?”
If I properly get Paul’s argument, he’s saying that both Jew and Gentile alike will be judged according to the light they have. Contrary to what many professing Jews claim today, the Jew derives no benefit from his circumcision and Law if there’s disobedience. Jews are justly condemned, for even though they have Scriptures’ light, they neglect it and thus demonstrate they are not really God’s covenant people. They are “nominal” Jews (i.e., Jewish in name only, not in practice).
This also applies to us who call ourselves Christians but in practice are worse than non-believers. God is serious about obedience to His commands and to think otherwise is to think contrary to the gospel message. For true faith produces obedience, while imperfectly, nevertheless obedience is the fruit.
How does the Gentile judge the Jew in this context? Perhaps by exposing their hypocrisy by obeying Gods’ law. For the Gentile, though not having the LAW does it, which shows that they are a covenant person and judge of the Jew as a result. This is what it seems Paul is saying (E.g., consider Jesus’ parable of The Good Samaritan to the Jews). Paul continues and says:
“28 For he is not a Jew who is one outwardly, nor is circumcision that which is outward in the flesh. 29 But he is a Jew who is one inwardly; and circumcision is that which is of the heart, by the Spirit, not by the letter; and his praise is not from men, but from God.”
Paul is clearly saying here, that outward signs—circumcision—without corresponding obedience to God—shows it’s a counterfeit faith, not produced by the Spirit of God. Mere religious observance is meaningless before Heavens’ court if the circumcision of the heart hasn’t taken place via the Spirit of truth which is what produces obedience that honors God. Here, Jewishness seems to equal the letter of the Law which is void of God’s life evidenced by the praise of men.
In a nutshell, Paul is saying that everything the Jews are trusting in that does not conform to the revelation of Jesus Christ in Paul’s gospel is not from God, the author of the Ten Commandments, but from the creature who suppresses the truth of God in unrighteousness.
The theme of pride here surfaces between Jew and Gentile. Paul is telling the Jew that religious pedigree is worthless if it’s not accompanied by obedience to the Law for the real Jew is not just a hearer of the word but also a doer of it. If the doing is not evidenced, deception has a chokehold on the individual.
Up to this point, the people of the Book of Scripture and of Nature are guilty before God because of their suppressing the truth of God in unrighteousness. Therefore their condemnation is just. So if the Jew disobeys the Law there’s no profit for them or the rest of humanity. Knowing this, it’s understandable why Paul was not ashamed of the gospel for it alone can rescue rebels from God’s wrath. Thus the target group for said news is all mankind.