Then the Lord spoke his word to Abram: “He will not be the one to inherit what you have. You will have a son of your own who will inherit what you have.”
You are descendants of the prophets. You have received the agreement God made with your ancestors. He said to your father Abraham, ‘Through your descendants all the nations on the earth will be blessed.’
Abraham’s son from the slave woman was born in the normal human way. But the son from the free woman was born because of the promise God made to Abraham.