Circumcision has value if you observe the law, but if you break the law, your circumcision has become uncircumcision.
25. For circumcision indeed profits, etc. He dissipates by anticipation what the Jews might have objected in opposition to him in the defense of their own cause: for since circumcision was a symbol of the Lord’s covenant, by which he had chosen Abraham and his seed as his peculiar people, they seemed not to have gloried in vain; but as they neglected what the sign...
In the latter part of the chapter the apostle directs his discourse more closely to the Jews, and shows what sins they were guilty of, notwithstanding their profession and vain pretensions. He had said (Rom 2:13) that not the hearers but the doers of the law are justified; and he here applies that great truth to the Jews. Observe, I.
Commenting on Romans 2:17-29
And shall not uncircumcision which is by nature,.... That is, the Gentiles, who are by nature uncircumcised; for as circumcision was by the command of God, and performed by the art of men, uncircumcision is by nature, and what men naturally have.