Romans 2:29 No, a man is a Jew if he is one inwardly; and circumcision is circumcision of the heart, by the Spirit, not by the written code. Such a man’s praise is not from men, but from God.
The director of the Jews For Jesus evangelistic organization, Moishe Rosen, always enjoyed using humor to make a point about religious truth. He has said that being raised in the church does not make you a Christian any more than being raised in a bakery makes you a bagel. Paul says to the Jews that being raised under the law and being circumcised in the body does not make you a child of God.
Our relationship to God is not based on external signs or appearances. God can go beyond the outside appearances and turn us inside-out, bearing our hearts, souls and innermost thoughts. In these places God can see our real relationship to Him.
Circumcision was a sign of obedience for the Jew. It was a permanent mark which separated Him from the rest of the world. But God doesn’t want just our bodies marked and set apart. He wants our hearts, our souls, our minds and our lives marked and changed by his Holy Spirit’s presence.
People joke about blurting our embarrassing tales under the influence of “truth serum”. Imagine the horror of having ALL your thoughts and the truth about ALL your actions poured out to the public. We would be horrified at such an occurrence. Yet, day in and day out we fail to realize that God sees them daily. That is why He wants to change us inside first so that our inner most nature might be healed and our outward actions would begin to reflect His Son.