Genesis 17:6 (KJV)

And when Abram was ninety years old and nine, the LORD appeared to Abram, and said unto him, I am the Almighty God; walk before me, and be thou perfect.

And I will make my covenant between me and thee, and will multiply thee exceedingly.

And Abram fell on his face: and God talked with him, saying,

As for me, behold, my covenant is with thee, and thou shalt be a father of many nations.

Neither shall thy name any more be called Abram, but thy name shall be Abraham; for a father of many nations have I made thee.

And I will establish my covenant between me and thee and thy seed after thee in their generations for an everlasting covenant, to be a God unto thee, and to thy seed after thee.

And I will give unto thee, and to thy seed after thee, the land wherein thou art a stranger, all the land of Canaan, for an everlasting possession; and I will be their God.

And God said unto Abraham, Thou shalt keep my covenant therefore, thou, and thy seed after thee in their generations.

This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised.

And ye shall circumcise the flesh of your foreskin; and it shall be a token of the covenant betwixt me and you.