Genesis 17:9

5 No longer will you be called Abram, but your name will be Abraham, for I have made you a father of many nations.

6 I will make you exceedingly fruitful; I will make nations of you, and kings will descend from you.

7 I will establish My covenant as an everlasting covenant between Me and you and your descendants after you, to be your God and the God of your descendants after you.

8 And to you and your descendants I will give the land where you are residing—all the land of Canaan—as an eternal possession; and I will be their God.”

9 God also said to Abraham, “You must keep My covenant—you and your descendants in the generations after you.

10 This is My covenant with you and your descendants after you, which you are to keep: Every male among you must be circumcised.

11 You are to circumcise the flesh of your foreskin, and this will be a sign of the covenant between Me and you.

12 Generation after generation, every male must be circumcised when he is eight days old, including those born in your household and those purchased from a foreigner—even those who are not your offspring.

13 Whether they are born in your household or purchased, they must be circumcised. My covenant in your flesh will be an everlasting covenant.

Read all of Genesis 17