Circumcision: The token of the covenant

9And God said unto Abraham, Thou shalt keep My covenant therefore, thou, and thy seed after thee in their generations. 10This is My covenant, which ye shall keep, between Me and you and thy seed after thee; Every man child among you shall be circumcised. 11And ye shall circumcise the flesh of your foreskin; and it shall be a token of the covenant betwixt Me and you. 12And he that is eight days old shall be circumcised among you, every man child in your generations, he that is born in the house, or bought with money of any stranger, which is not of thy seed. 13He that is born in thy house, and he that is bought with thy money, must needs be circumcised: and My covenant shall be in your flesh for an everlasting covenant. 14And the uncircumcised man child whose flesh of his foreskin is not circumcised, that soul shall be cut off from his people; he hath broken My covenant. 15And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be. 16And I will bless her, and give thee a son also of her: yea, I will bless her, and she shall be a mother of nations; kings of people shall be of her. 17Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is an hundred years old? and shall Sarah, that is ninety years old, bear? 18And Abraham said unto God, O that Ishmael might live before thee! 19And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish My covenant with him for an everlasting covenant, and with his seed after him. 20And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation. 21But My covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year. 22And He left off talking with him, and God went up from Abraham. Genesis 17