Genesis 17:12-13

12And every male among you who is 1eight days old shall be circumcised throughout your generations, including a slave who is born in the house or who is bought with money from any foreigner, who is not of your 2descendants.

13A slave who is born in your house or 3who is bought with your money shall certainly be circumcised; so My covenant shall be in your flesh as an everlasting covenant.