For circumcision - John 7:22 note; Acts 7:8 note. This was the special rite by which the relation to the covenant of Abraham was recognised; or by which the right to all the privileges of a member of the Jewish commonwealth was acknowledged. The Jews of course affixed a high importance to the rite.
Verily profiteth - Is truly a benefit; or is an advantage. The meaning is, that their being recognised as members of the Jewish commonwealth, and introduced to the privileges of the Jew, was an advantage; see Romans 3:1-2. The apostle was not disposed to deny that they possessed this advantage, but he tells them why it was a benefit, and how it might fail of conferring any favor.
If thou keep the law - The mere sign can be of no value, The mere fact of being a Jew is not what God requires. It may be a favor to have his Law, but the mere possession of the Law cannot entitle to the favor of God. So it is a privilege to be born in a Christian land; to have had pious parents; to be amidst the ordinances of religion; to be trained in Sundayschools; and to be devoted to God in baptism: for all these are favorable circumstances for salvation. But none of them entitle to the favor of God; and unless they are improved as they should be, they may be only the means of increasing our condemnation; 2 Corinthians 2:16.
Thy circumcision is made uncircumcision - Thy circumcision, or thy being called a Jew, is of no value. It will not distinguish you from those who are not circumcised. You will be treated as a pagan. No external advantages, no name, or rite, or ceremony will save you. God requires the obedience of the heart and of the life. Where there is a disposition to render that, there is an advantage in possessing the external means of grace. Where that is missing, no rite or profession can save. This applies with as much force to those who have been baptized in infancy, and to those who have made a profession of religion in a Christian church, as to the Jew.