Then one of them said, “I will return to you about this time next year, and your wife, Sarah, will have a son!” Sarah was listening to this conversation from the tent.
And I will bless her and give you a son from her! Yes, I will bless her richly, and she will become the mother of many nations. Kings of nations will be among her descendants.”
But God replied, “No—Sarah, your wife, will give birth to a son for you. You will name him Isaac, and I will confirm my covenant with him and his descendants as an everlasting covenant.
The son of the slave wife was born in a human attempt to bring about the fulfillment of God’s promise. But the son of the freeborn wife was born as God’s own fulfillment of his promise.