Romans 9:6-9, The Word of Promise Will Be Fulfilled
In Genesis 17:19 (KJV), God said to Abraham, 19 … Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.” God will cause Sarah’s barren womb to be opened in her old age to bring forth this son of the covenant. Even the name of this child was given by God. This is the son Isaac through whom will fulfil God’s covenant with Abraham. At that time, Abraham had another son Ishmael who came from the womb of Sarah’s handmaid Hagar. Ishmael was not the son of promise. He came because Abraham and Sarah did not trust God and with impatience sought to “help God” fulfil His promise. God clarified with Abraham that Ishmael is not the son of promise that will bring forth the Messiah but Isaac.