But God said, “No. Your wife Sarah will bear you a son and you will name him Isaac. I will keep my covenant with him and with his descendants forever. It is an everlasting covenant.
I will bless her, and I will give you a son by her. I will bless her, and she will become the mother of nations, and there will be kings among her descendants.”
“I will keep my promise to you and to your descendants in future generations as an everlasting covenant. I will be your God and the God of your descendants.
Live here, and I will be with you and bless you. I am going to give all this territory to you and to your descendants. I will keep the promise I made to your father Abraham.
It was faith that made Abraham able to become a father, even though he was too old and Sarah herself could not have children. He trusted God to keep his promise.