Exodus 12:44
But any slave a man has purchased may eat it, after you have circumcised him.
Genesis 17:12-13
Throughout your generations, every male among you at eight days old is to be circumcised.
Genesis 17:23
Then Abraham took his son Ishmael and all the slaves born in his house or purchased with his money—every male among the members of Abraham’s household—and he circumcised the flesh of their foreskin on that very day, just as God had said to him.