"Circumcision" is a surgical procedure. It is a removal of skin. God commanded Israel to follow this procedure to make them district from the people groups around them.
But it is not obvious. You can't walk down the street and see that someone is circumcised; and that someone else is not. God directed Israel to institute an un-obvious distinction.
If God wanted everyone to see this distinction, he would have done something else. Israel would have had a different hairstyle or clothing. The distinction is not obvious for a purpose. The distinction is communicated to the hearts of Israel. Distinction based on undergoing a surgical procedure is no different than a distinction based on a different hairstyle. If it doesn't get into the heart, there is no difference.
The distinction was not obvious, but each Jew knew it was there. And that was the point. It was intended to create that awareness. The mark in the flesh was designed to make a mark in the heart.
● God's Perspective
Israel was chosen as God's people to demonstrate his character to the world. God worked in Israel's history, in their culture, so he would become more real, and his works would become more real. As he becomes more real, more solid, we learn to lean on him, trust in him, and live in obedience to him. We confidently live out his purposes.
Does God want us to speak to those, who have no relationship with him, about him? Of course he does. When was the last time? When it comes down to it, there are very few reasons why people do not obey God in this. It comes down to love (God and people) and trust (God).
I am not accusing. I am just as guilty. It is just obvious that if we loved him, knew and trusted him, and believed what he said, we would move naturally into situations where revealing Jesus to people would be as easy as falling off a log, as simple as ABC, and as natural as organic granola.
● Living My Life
Scripture says anyone, who gives his allegiance to Jesus, is circumcised with Christ -- whether they have undergone the surgical procedure or not. Anyone in Christ undergoes a procedure of the heart. There is a removing of "flesh" from the heart.
The process of being identified in Christ's death (crucifiction, burial and resurrection) is a metaphor of how sin's power is crushed in our lives. Circumcision is another metaphor of sin's defeat. Just as flesh is removed from a human body, sin's power is also separated from us.
We will always live with sin's presence. We will unfortunately also sin. But without the defeat of its power, any hope of growth is in vain.
The penalty of sin is paid. The power of sin is defeated. Only the presence of sin remains. It will be defeated, but only in the fullness of God's kingdom.
We now have the authority to choose. We can choose love, trust and obedience. We can choose humility and generosity. Right choices breed right choices. Which breeds right character. Which breeds fruit in our lives and the lives of others.