All of the people of God are marked with a special brand as it were. In the Old Testament, circumcision was the proof of divine ownership. It was required of all make children of the people of Israel, as well as of all male converts or proselytes. It was an external sign of the covenant which made them God’s people. It was also a subjective sign of the covenant in that it was applied individually to each person, whereas the ark of the covenant served as an objective sign for the whole group.
Instead of this external circumcision of the flesh, found in the administration of the old covenant, we find under the new covenant an inward circumcision of the heart. Paul wrote, “He is a Jew who is one inwardly, and real circumcision is a matter of the heart, spiritual and not literal” (Romans 2:29; see also Philippians 3:3)
– Erickson, Millard
as quoted by Driscoll, Mark and Gary Breshears, Vintage Church: Timeless Truths and Timely Methods, Crossway Books, Wheaton, IL, 2008, p.