"There truly IS ONE BAPTISM in this dispensation. ANd it has nothing to do with water."
"Water baptism can NOT be the One Baptism Paul writes of for us today. "For BY ONE SPIRIT are we all baptized INTO ONE BODY.,.."1 Cor. 12:13. Not physically, Spiritually."
Good stuff. However, I am still curious about your original question. Why was circumcision used? Call me crass, but how does the alteration of certain bodily components (especially THAT component) mean so much? No one should see the alteration, save for a spouse. Why would God give this to Abraham (Gen. 17)? It has always puzzled me.
Circumcision has always puzzled me, too. All we are told about it is that circumcision was the outward show of faith that GOd commanded and the Abrahamic Covenant with circumcision as a show of faith was the “sign” that was given by God to Abraham to perform, not only to separate him and his seed from the ungodly world of the Gentiles, but also as a “seal” of the righteousness of faith. (Rom. 4:11). Also, and mainly, as a token of God’s covenant with him. (Gen. 17:11). The covenant being that Abraham’s multiplied seed (later called “the Circumcision”) was to become a blessing to all nations. That’s all I know about it, but it is a very interesting topic, I think.