Genesis 17:10

The token of the covenant is circumcision, for the sake of which, the covenant is itself called the covenant of circumcision, Acts 7:8. It is here said to be the covenant which Abraham and his seed must keep, as a copy or counterpart. It is called a sign and seal, (Romans 4:11,) for it was, 1st, A confirmation to Abraham and his seed of those promises which were God's part of the covenant, assuring them that, in due time, Canaan should be theirs: and the continuance of this ordinance, after Canaan was theirs, intimates that that promise looked further, to another Canaan. 2d, An obligation upon Abraham and his seed to that duty which was their part of the covenant, not only to the duty of accepting the covenant, and putting away the corruption of the flesh, which were primarily signified by circumcision, but in general to the observation of all God's commands. They who will have God to be to them a God, must consent to be to him a people.