Genesis 17:9-10

17:9 Then God said to Abraham, “As for you, you must keep the covenantal requirement I am imposing on you and your descendants after you throughout their generations. 17:10 This is my requirement that you and your descendants after you must keep: Every male among you must be circumcised.

Genesis 17:19

17:19 God said, “No, Sarah your wife is going to bear you a son, and you will name him Isaac. I will confirm my covenant with him as a perpetual covenant for his descendants after him.