Genesis 17:1-11 NIV
When Abram was ninety-nine years old, the LORD appeared to him and said, “I am God Almighty; walk before me faithfully and be blameless. Then I will make my covenant between me and you and will greatly increase your numbers.”
Abram fell facedown, and God said to him, “As for me, this is my covenant with you: You will be the father of many nations. No longer will you be called Abram; your name will be Abraham, for I have made you a father of many nations. I will make you very fruitful; I will make nations of you, and kings will come from you. I will establish my covenant as an everlasting covenant between me and you and your descendants after you for the generations to come, to be your God and the God of your descendants after you. The whole land of Canaan, where you now reside as a foreigner, I will give as an everlasting possession to you and your descendants after you; and I will be their God.”
Then God said to Abraham, “As for you, you must keep my covenant, you and your descendants after you for the generations to come. This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised. You are to undergo circumcision, and it will be the sign of the covenant between me and you.
NIV: New International Version