Genesis 17:11 BBE

⁹  And God said to Abraham, On your side, you are to keep the agreement, you and your seed after you through all generations.

¹⁰  And this is the agreement which you are to keep with me, you and your seed after you: every male among you is to undergo circumcision.

¹¹  In the flesh of your private parts you are to undergo it, as a mark of the agreement between me and you.

¹²  Every male among you, from one generation to another, is to undergo circumcision when he is eight days old, with every servant whose birth takes place in your house, or for whom you gave money to someone of another country, and not of your seed.

¹³  He who comes to birth in your house and he who is made yours for a price, all are to undergo circumcision; so that my agreement may be marked in your flesh, an agreement for all time.