Genesis 17 is a pretty significant chapter. We could summarize the story of the entire Bible by starting here. A general survey of Christianity could start here. God gives Abram the covenant of circumcision, and then foretells the birth of Issac. Let’s deal with circumcision in this setting.
In the ancient world names meant something. I’ve looked up Clark in the books, and my name means either scholar or clergy. I like my name. Well, I like my first name. My last name, Bunch, means person with a humpback. You can’t win ’em all. At any rate, Abram literally means father. Abram has already believed God’s promise that he will father an entire nation, or in fact many nations. Abram’s name gets changed by God to Abraham, which is father of many. His name, which already meant something, now means something even greater.
Then God explains the rite of circumcision, and that it will be an outward sign of the people of faith. Two things to remember here; one is that a lot of Judaism had to do with being different from the rest of the world. This included outwardly in appearance and behavior, in addition to their faith and belief system. Circumcision was a sign. It made them physically different, like the beards and not cutting the hair of the temples. The statement is mentioned here and many other times (like when the 10 commandments are being given) that Abraham’s family will be God’s people and he will be their God. Circumcision is an outward sign of the covenant relationship.
The other thing to remember is that the Old Testament makes a lot more sense after reading the New. The Passover story, the whole sacrificial system, those are just scary stories until we read the Gospels. Then we go “Oh, I get it now.” After reading the history of the Jews and learning over and over about a vengeful and jealous God, being offered mercy and grace really means something. When a person gets saved, is that saved from sin, saved from hell, saved from death? No, salvation is about being saved from God’s wrath. God’s wrath was poured out on Jesus as he hung on the cross, so that we never have to receive it. The Old Testament helps us appreciate the Gospel for what it’s worth. Under the New Covenant, baptism is the outward expression of our faith. Baptism is to the New Testament church what circumcision was to the Hebrews; the outward expression of faith. They were the children of Abraham, we are spiritually the children of Abraham. We are a holy nation, a royal priesthood, but not made up of any one political nation. The descendants of Abraham made up the nation of Israel, the people of the New Testament church are the Kingdom of God not made with hands. They were God’s people, we are God’s people.
I can’t discuss or teach the Old Testament in a vacuum; the New Testament is like the magic decoder ring that makes the symbols and images make sense. Just like Passover became the Lord’s supper, circumcision in the equivalent of baptism. Hopefully this answers some questions. If not, go ahead and ask them. I’m game.