God made a covenant or agreement with Abraham which included the multiplying of Abraham’s descendants, giving them the land of Canaan (basically modern-day Israel) and He being their God (Gen 17:1-27). Abraham’s side of the deal was to obey and walk uprightly before God. To signify Abraham’s acceptance of the terms each Jewish male was to be circumcised – traditionally performed on eight-day-old boys when the foreskin of the penis was cut away. It was an outward symbol, of great spiritual significance as it distinguished the Jewish nation from the uncircumcised (Gentile) nations. In the OT refusing circumcision was to cut oneself off from God’s blessing (Gen 17:14).
Heart circumcision involves being fully identified with Him
and life to God and not resisting Him for “Keeping God’s commands is what counts” as this is the outworking of our love for Him (Deut 10:16, 30:6; Jer 4:4; Jn 14:15; 1 Cor 7:19; Col 2:11). The Bible states a person is a ‘real Jew’ (part of God’s family) if they are circumcised in heart, not born into the race and follow its customs (Rom 2:28,29; Phil 3:3).
While other cultures also practice circumcision (often as an initiation to adulthood at puberty), only to the Israelites does it signify being God’s people. Christians are not under the OT law and so it is not required, however, today circumcision among non-Jews is still done on newborns in some cultures for health and medical reasons.