Why did God choose to make circumcision the covenant sign of Israel?
When people made covenants in ancient times, they often would perform a covenant sign to remind each other what would happen if either party broke the covenant. In the case of Israel – do not think too hard about this – God required every male Israelite to have a small, sensitive part of their body cut off. They were declaring that if the nation broke covenant with God through habitual disobedience, God, in his perfect justice, ought to cut them off from him, each other, and even life itself.
Just as Israel habitually broke the covenant that God made with them through Moses, we all have disobeyed God’s holy law. God’s justice requires we be cut off. Yet, Jesus allowed himself to be cut off for our behalf, so that we would not need to.
Jesus did even more than this. In Deuteronomy 10:16, God commanded the Israelites to circumcise not only their flesh but their heart. Without an inward disposition of love and obedience toward God, the covenant sign of circumcision became meaningless (Romans 2:25). It would be like being baptized as a baby yet never confirming that baptism later in life through belief in Christ. That baptism would become meaningless.
In the prophetic section of Deuteronomy, God reveals that at an undisclosed time in the future Israel would break their covenant with God (Deuteronomy 30:1). This would lead to being exiled to a foreign land. Yet, God promised that one day he would do what they failed to do, circumcise their hearts (Deuteronomy 30:6).
That day came in Christ. While we can do nothing to contribute to our salvation – Christ did that when he was cut off instead of us – we can cooperate with God’s process of sanctification.
A person receives the gift of the Holy Spirit the moment they believe. The Holy Spirit begins the tender surgery of gradually cutting away our stubbornness toward God. This work of sanctification does not operate like a motor in a car, without which the car could not move. Rather, like one person cooperating with another, the Holy Spirit enters the believer’s heart and allows him or her to live a holy, obedient life unto God.
There is a love that God wants to well up in the heart that trusts in him. He wants us to love him with unbridled devotion. He wants us to relish in his laws and ways. He wants us to experience the joy of living holy, obedient lives unto him. He will circumcise the hearts of those who trust in him.