Circumcision was usually practiced in the ancient world as a rite of passage into puberty or marriage, though it does not seem to have been practiced among the Canaanites. God, however, gave this peculiar custom new meaning when he required it of Abraham. For Abraham, circumcision was a mark of possession, indicating that he belonged to God. It was also a sign of commitment, symbolizing that the Lord alone would be the one he would trust and serve. Some think it indicated a type of oath: “May I be cut off from my people as my foreskin has been cut off, if I am not faithful to the Lord (Gen. 17:14).
In many ways, God’s relationship with Abraham, as symbolized by circumcision, is similar to that of a marriage covenant. The commitment that God intends a husband and a wife to have for each other illustrates the commitment that God wanted from Abraham. Throughout the Old Testament, God characterizes himself as a husband to his people, and adultery is used as a metaphor for their idolatry and unfaithfulness to him (see, for example, Hosea 2:16; 4:15).
–The Quest Study Bible