Romans 2:25-29

²⁵ For circumcision is indeed profitable if you keep the law; but if you are a breaker of the law, your circumcision has become uncircumcision.

²⁶ Therefore, if an uncircumcised man keeps the righteous requirements of the law, will not his uncircumcision be counted as circumcision?

²⁷ And will not the physically uncircumcised, if he fulfills the law, judge you who, even with your written code and circumcision, are a transgressor of the law?

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 of the heart, in the Spirit, not in the letter; whose praise is not from men but from God.

Circumcision was the seal of God’s covenant.

Circumcision didn’t justify, but it did profit if a person kept the law (in the sense of endeavoring to keep it, not perfection). But since nobody does perfectly keep the law, so circumcision doesn’t help save.

To be a Jew, one had to be (1) born of Abraham through Isaac and (2) spiritually in good standing with God (circumcision of the heart).

Righteousness of the law (v.26) — an effort to obey one’s conscience

Inwardly (v.29) = literally “in secret” — not obeying the Law for show

Don’t be circumcised (in an attempt to obey the Law) unless you plan to follow the entire Law. For I testify again to every man that is circumcised, that he is a debtor to do the whole law (Galatians 5:3).

But instead … We are the circumcision, which worship God in the spirit, and rejoice in Christ Jesus, and have no confidence in the flesh (Philippians 3:3).

In the spirit, not in the letter (v.29) — The NKJV capitalizes “Spirit,” making it a reference to the Holy Spirit. But Old Testament believers weren’t indwelled with the Spirit—He only came upon certain people for certain lengths of time to perform certain tasks. I think it’s possible that “spirit,” here, refers to the motivation of the person obeying the law—whether they do it by faith, or as a checklist. Although that still leaves a question about what Jesus was talking about to Nicodemus in John 3:3-6 (My notes on that passage are not particularly helpful) :

³ Jesus answered and said to him, “Most assuredly, I say to you, unless one is born again, he cannot see the kingdom of God.”

⁴ Nicodemus said to Him, “How can a man be born when he is old? Can he enter a second time into his mother’s womb and be born?”

⁵ Jesus answered, “Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God.

⁶ That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.