Genesis 17:12-13

And euery man childe of eight dayes olde among you, shalbe circumcised in your generations, aswell he that is borne in thine house, as he that is bought with money of any stranger, which is not of thy seede. He that is borne in thine house, and he that is bought with thy money, must needes be circumcised: so my couenant shall be in your flesh for an euerlasting couenant.