But God told Abraham, “Don't feel bad about the boy and the slave woman. Do whatever Sarah tells you, because it's through Isaac that your descendants will be counted.
“No, it's your wife Sarah who is going to have a son for you!” God replied. “You are to call him Isaac. I will keep my agreement with him and his descendants as an eternal agreement.
I make known the end from the very beginning, declaring from ancient times what the future will bring. Whatever I plan will take place; I will accomplish everything I wish.
But what does Scripture say? “Send away the servant girl and her son, for the son of the servant girl will not be an heir together with the son of the free woman.”