12 All who sin apart from the law will also perish apart from the law, and all who sin under the law will be judged by the law. 13 For it is not those who hear the law who are righteous in God’s sight, but it is those who obey the law who will be declared righteous. 14 (Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law. 15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.) 16 This will take place on the day when God judges people’s secrets through Jesus Christ, as my gospel declares.
The gospel declares that the only person who will be saved are the people who would obey the law. This is bad news because obeying the law in its totality is impossbile. Nobody is perfect. So if nobody is perfect, then everybody deserves hell. Now that is a big problem. The Jews had this problem. They think they were holier than the others so Paul had to remind them of the truth in light of the holiness of God.
17 Now you, if you call yourself a Jew; if you rely on the law and boast in God; 18 if you know his will and approve of what is superior because you are instructed by the law; 19 if you are convinced that you are a guide for the blind, a light for those who are in the dark, 20 an instructor of the foolish, a teacher of little children, because you have in the law the embodiment of knowledge and truth— 21 you, then, who teach others, do you not teach yourself? You who preach against stealing, do you steal? 22 You who say that people should not commit adultery, do you commit adultery? You who abhor idols, do you rob temples?23 You who boast in the law, do you dishonor God by breaking the law? 24 As it is written: “God’s name is blasphemed among the Gentiles because of you.”
Paul was saying, JEWS, don’t even think you are holier than the others. In fact you have blasphemed the name of God because of your legalism. You think by obeying the law, you are more special. You think because of your circumcision, you are better Christians. You got it all wrong.
25 Circumcision has value if you observe the law, but if you break the law, you have become as though you had not been circumcised. 26 So then, if those who are not circumcised keep the law’s requirements, will they not be regarded as though they were circumcised? 27 The one who is not circumcised physically and yet obeys the law will condemn you who, even though you have the[c] written code and circumcision, are a lawbreaker.
28 A person is not a Jew who is one only outwardly, nor is circumcision merely outward and physical. 29 No, a person is a Jew who is one inwardly; and circumcision is circumcision of the heart, by the Spirit, not by the written code. Such a person’s praise is not from other people, but from God.
Paul then points the Jews back to the heart of the gospel. The circumcision is not a circumcision of your sexual organ – it is a circumcision of the heart. The cutting of the flesh by the Spirit of God – not by what you do for God. It is God’s handiwork not yours. You bring nothing to the table but your sin. God did the work. Jesus died for our sin. Jesus declares it is finished. You have no part to play.