When I was much younger, I used to think that I was circumcised because my parents were Christians, and as a result had me circumcised because our father Abraham was commanded to circumcise his children as a sign of the covenant God had with him. I know better now though.
The concept of circumcision is older than recorded history. Scholars would have us believe that the practice of circumcision was in place before Abraham, though it was not quite the common practice at that time. The question of why and how circumcision came to be a thing has not been answered.
But perhaps, a more interesting question would be; why did God ask Abraham to undertake (and pass down to future generations) the painful, strange, and emasculating (as some cultures viewed it in Abraham’s time) procedure of circumcision. We have a part of our answer in Genesis 17.
“This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised. You are to undergo circumcision, and it will be the sign of the covenant between me and you.”Genesis 17:10-11 (NIV)
In the covenant that God brought Abraham into, circumcision of the foreskin was the sign of belonging, the sign of the chosen, the sign that he and his descendants were set apart from the rest of the world to be in a special howbeit somewhat strained relationship with God.
The Bible is a book of progressive revelation. As God spoke more and more through the prophets of old, and then explained all of the mystery of the “Old Testament” to us through the epistles, the true significance of that physical circumcision becomes clearer to us.
In Him you were also circumcised with a circumcision not made with hands, but by the [spiritual] circumcision of Christ in the stripping off of the body of the flesh [the sinful carnal nature].Colossians 2:11 (AMP).
As Abraham is the foreshadowing of being accepted into God by Faith alone and not by works, it is the same way the circumcision of then is a foreshadowing of how God now seeks to separate His chosen ones from the rest of the world by performing a circumcision not made by human hands on the foreskin of our hearts.
A spiritual procedure that changes us from the inside, and enables us to live lives that please God and is appreciable to people, the same way a circumcised phallus is easily differentiated from an uncircumcised one.
Notice how the command for Abraham to become circumcised came after he had been declared righteous by God? (Romans 4:11). That inward change that births the outward can only fully and consistently manifest after we let God perform the full work of circumcision on our hearts.
We live right before God because He has made us (believers) right before Him, not because we are trying to be right before Him.