It does not matter if we follow all the rituals of Christianity perfectly; if the sinfulness of our hearts has not been cut off, our condemnation is justified. We cannot be children of God outwardly only. A child of God is one inwardly.
Paul tells the Romans this very truth. He says, “For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical, but a Jew is one inwardly, and circumcision is a matter of the heart, by the Spirit, not by the letter (Romans 2:28-29).
This truth is significant because you could be a Jew outwardly but not truly be a Jew. Even if a man in the Old Covenant had the mark of circumcision on his body, the sign of the covenant, he could still be entirely cut off from God himself.
When Paul says circumcision is a matter of the heart, he is telling us our hearts must be changed. It is possible to participate in all of Christianity’s rituals and rites and follow the Ten Commandments and not be a Christian. All of this can be done for our glory, not God’s.
This desire for self-glory is our natural state; we are self-seeking people. Paul calls this sinful disposition the “flesh” later in Romans. The problem with our sinful nature is we cannot cut it off ourselves. Not even following the law of God will get it done. Even if we could begin to fulfill the law of God, the minute we did it, we would start to boast and look at ourselves with pride.
The cutting of the flesh in circumcision is an outward picture of the severing of the sinfulness of our hearts, but how can our sinful nature be cut off if following the law of God cannot accomplish it? The Spirit of God must do it (Romans 2:29).
John calls this the new birth or receiving spiritual life. We are spiritually dead, but when we are born again by the Spirit of God, our hearts stop looking to ourselves for salvation and, through faith, look to Christ’s work on the cross and his resurrection.
Here is the astounding thing about the new birth. The Spirit tells us to stop obeying the law of God to find salvation, but when we are born again, he does not move us to abandon the law; he causes us to love it. Instead, we follow it because we want to see God glorified. Not because we are seeking self-glory.
The question remains, is this us? Have we been circumcised of heart? Have we been born again, or are all our rituals outward because we enjoy the earthly benefits they bring? For those who follow the Christian life outwardly only, there will be wrath and fury, but those who have been circumcised of heart have eternal life.