WHY CIRCUMCISION? Why not a tattoo on the arm or something similar? Circumcision was a hidden sign. It seems to me it has something to do with the promise of Abraham having many descendants, being fruitful and multiplying. The sign reaffirms God's promise right at the very place where the sexual act takes place. It marks the sexual act as set apart for God's purposes. It reminds me that God has authority over me even in the most private aspects of my life. He designed me and set me apart for sex within the context of my marriage, with my wife alone.
Circumcision is seen by some people today as MUTILATION. Some doctors refuse to do the operation. God was looking for obedience but NOT JUST OBEDIENCE. He wanted Abraham's HEART.
Romans 2:28-29 (NLT) says "For you are not a true Jew just because you were born of Jewish parents or because you have gone through the ceremony of circumcision. No, a true Jew is one whose heart is right with God. And true circumcision is not merely obeying the letter of the law; rather, it is a change of heart produced by God's Spirit. And a person with a changed heart seeks praise from God, not from people."