From here to the end of the chapter the Jews were especially addressed in order to show that all of their external advantages over the Gentiles, such as the Law, the ceremony, the prophets, and so forth, would not justify them before God! They were sinners like the Gentiles, and trusting in these external types and privileges only aggravated their condemnation.
(Vs. 17-20) In these four verses Paul deals with the privileges of the Jews under six particular headings.
(1) "You bear the name of Jew." They were Abraham's seed. In that name they were distinguished from all other nations and people.
(2) "You rest in the Law." It was not that they loved the Law, or obeyed it, or understood the purpose of it, or saw Christ as the end and goal of it for righteousness, but only that they had the Law and the ceremony and, therefore, claimed God's favor and blessings.
(3) "You boast that the true God is your God." The Gentiles worshipped idols; the Jews worshipped the true God. The Gentiles were aliens; the Jews were the covenant people. The Gentiles had no prophets nor tabernacle; God dwelt with the nation of Israel.
(4) "You say that you know God's will." What He requires, what He commands, and what is agreeable to Him.
(5) "You say that you approve of the things of God because you have been instructed by the Law."
(6) "You say that you are guides and teachers of other men." They felt that they had in their Law the embodiment of knowledge and truth, which equipped them to be teachers and instructors.
(Vs. 21-23) In these verses Paul reveals their hypocrisy. He establishes more firmly what he had said earlier in this chapter that, though they had the Law, they did not practice it; and though they boasted of their knowledge of the Law, they were ignorant of its spirituality and therefore condemned themselves (Rom. 10:1-4).
Here is a man who says he is one of God's chosen people, who has received and approved of the Law, whose boast is in God, who knows His will, approves of the excellent things, who teaches others that they should not steal, lie, commit adultery, or worship idols. Surely this is a man of God! He would have you believe that he is. But under this mask of hypocrisy is a thief, an adulterer, a blasphemer, and an idolator who makes a mockery of the Law by continually breaking it.
Whatever advantage the Jews had over the Gentiles, they were, notwithstanding, in the same condition before God–unrighteous, ungodly, intemperate, and consequently subjected to the same condemnation. (Vs. 24) It is written by your prophets that wherever you journeyed among the Gentiles, your conduct and behavior caused the heathen to mock the name of God (Ezek. 36:20-22; II Sam. 12:13-14).
(Vs. 25) Paul here pursues the Jew into his last stronghold, CIRCUMCISION! This rite was more ancient than Moses and distinguished them from other nations. Circumcision was a symbol of the Lord's covenant and a sign of all the advantages enjoyed by the Jews. They thought that circumcision itself was sufficient to obtain righteousness. Paul declares that in view of obtaining favor with God, circumcision is profitable only if you perfectly keep the whole Law (Gal. 5:2-3). If you are trusting the fact that you are circumcised to reconcile you to God and you do not keep the whole Law, you may as well be uncircumcised.
(Vs. 26-27) This is a hypothetical case, for no man can keep the whole Law. But suppose an uncircumcised man should keep the Law perfectly. He would be righteous before God, and he would condemn you who have the outward form and letter but transgress the Law.
(Vs. 28-29) A man is not a child of God, righteous before God, and justified by mere name, nationality, profession, and ceremony. True circumcision is not something outward, but it is an inward work of grace on the heart.
A man is a true Jew (or redeemed person) who has a work of grace in the heart, who has renounced his works and looked to Christ, who worships God in spirit and truth, who has the Law of God written on his heart and not in his hand, and his praise is from God and not from men (Psa. 34:18; Psa. 51:17).