A reader asked,

For a long-time circumcision in the Scriptures has annoyed me—not because it’s there—but because I don’t think I fully understand its meaning, though I’m clear on the meaning in relation to the anatomy. Am I correct to think that in some places, it is referring to the literal/physical procedure only? Am I correct to think that in others, the word is inclusive of a general lifestyle of law-keeping and is not limited to the literal/physical procedure? Could you steer me toward passages that answer these?

Yes, in some places, circumcision (as in “the circumcision of the heart”) is used figuratively. Yes, sometimes it just refers to the physical practice. 

The expression those of the circumcision in the NT refers to unbelieving Jews who believed that circumcision of Gentiles was necessary for salvation (Acts 15:1) and to believing Jews who believed it was necessary for sanctification, but not for salvation (Acts 10:45; 11:2; 15:5). As you say, those who believed that circumcision was necessary for salvation did not think just the physical act would guarantee one’s eternal salvation. They saw circumcision as a sign of the Law and thus they taught that one who was circumcised was committing himself to keeping the Law of Moses in order to keep his salvation (or in order to gain final salvation).

As for verses on circumcision, here are some of each type:

The following verses are just a small sample of those which deal with literal circumcision: Genesis 17:10-27; 21:4; 34:15-24; Exodus 4:26; 12:44, 48; Leviticus 12:3; Joshua 5:2-8; Luke 1:59; 2:21; John 7:22-23.

The following verses refer to circumcision of the heart, a figurative expression that refers to the need for a new spiritual mindset: Deuteronomy 10:16; 30:6; Jeremiah 4:4; Romans 2:28-29; Philippians 3:3; Colossians 2:11.

A book for which literal circumcision plays a major role is Paul’s letter to the Galatians. Works-salvation preachers were saying that in order to be justified before God a person had to not only believe in Christ, but also be circumcised and keep the law of Moses. We call these preachers Judaizers, since they were attempting to impose a faulty understanding of Judaism upon Christianity. See, for example, Gal 5:4. The believer who submits to circumcision thinking that it is necessary for his salvation falls from the present experience of God’s grace. He can’t lose everlasting life. But he can and does lose the experience of God’s favor in his daily living unless and until he repents of this heresy.