Genesis 17:9 And God said to Abraham, “As for you, you shall keep my covenant, you and your offspring after you throughout their generations. This is my covenant, which you shall keep, between me and you and your offspring after you: Every male among you shall be circumcised. You shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between me and you. He who is eight days old among you shall be circumcised. Every male throughout your generations, whether born in your house or bought with your money from any foreigner who is not of your offspring, both he who is born in your house and he who is bought with your money, shall surely be circumcised. So shall my covenant be in your flesh an everlasting covenant. Any uncircumcised male who is not circumcised in the flesh of his foreskin shall be cut off from his people; he has broken my covenant.”
God introduced the command regarding circumcision with these words. The cutting and removal of the foreskin of every male among Abraham’s covenant descendants would mark them as those who were in the covenant. Since this covenant was made with the literal, genetic descendants of Abraham through the promise of God, it was appropriate that this sign of the covenant be given to those born into the covenant and was associated with the reproductive part of their body. For the first time, God gave Abraham something to do in regard to the covenant. He told him that his descendants must take upon themselves a sign of the covenant, showing they received the covenant by faith. More importantly, circumcision is a cutting away of the flesh and an appropriate sign of the covenant for those who should put no trust in the flesh.
Those who rejected circumcision rejected the sign of the covenant. They were no friends of the covenant God made with Abraham. It wasn’t that circumcision made them a part of the covenant (faith did), but rejection of circumcision was a rejection of the covenant. Unfortunately, through the centuries, the Jews began to trust more in the sign of the covenant (circumcision) than in the God of the covenant, believing that circumcision by itself was sufficient and necessary to save. Paul refutes this idea extensively, especially in light of the finished work of Jesus. (Guzik)
