10 This is my covenant, which you shall keep, between me and you and your seed after you. Every male among you shall be circumcised. 11 You shall be circumcised in the flesh of your foreskin. It will be a token of the covenant between me and you. 12 He who is eight days old will be circumcised among you, every male throughout your generations, he who is born in the house, or bought with money from any foreigner who is not of your seed.

Matthew Henry's Commentary on Genesis 17:10-12

Commentary on Genesis 17:7-14

(Read Genesis 17:7-14)

The covenant of grace is from everlasting in the counsels of it, and to everlasting in the consequences of it. The token of the covenant was circumcision. It is here said to be the covenant which Abraham and his seed must keep. Those who will have the Lord to be to them a God, must resolve to be to him a people. Not only Abraham and Isaac, and his posterity by Isaac, were to be circumcised, but also Ishmael and the bond-servants. It sealed not only the covenant of the land of Canaan to Isaac's posterity, but of heaven, through Christ, to the whole church of God. The outward sign is for the visible church; the inward seal of the Spirit is peculiar to those whom God knows to be believers, and he alone can know them. The religious observance of this institution was required, under a very severe penalty. It is dangerous to make light of Divine institutions, and to live in the neglect of them. The covenant in question was one that involved great blessings for the world in all future ages. Even the blessedness of Abraham himself, and all the rewards conferred upon him, were for Christ's sake. Abraham was justified, as we have seen, not by his own righteousness, but by faith in the promised Messiah.