5 Theirs are the patriarchs, and from them is traced the human ancestry of the Messiah, who is God over all, forever praised! Amen. 6 It is not as though God’s word had failed. For not all who are descended from Israel are Israel. 7 Nor because they are his descendants are they all Abraham’s children. On the contrary, “It is through Isaac that your offspring will be reckoned.” 8 In other words, it is not the children by physical descent who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring. 9 For this was how the promise was stated: “At the appointed time I will return, and Sarah will have a son.” — Romans 9:5-9 NIV
The promise that God made to His friend, Abraham, was fulfilled. Abraham did become the Father of many nations through his first two sons, Ishmael was the frist born, a child concieved with Hagar ten years after the promise. It was another 13-14 years later before Isaac was born to Abraham and Sarah. It was sixty years later when Jacob (Israel) and Esau were born to Isaac and Rebekah. It was through Jacob that we trace the lineage of Jesus Christ. This promise was very slow in being fulfilled, but it was confirmed over and over throughout the Old Testament. Though Abraham did become the Father of many nations, the promise was not made regarding the physical descendants but, rather to the Spiritual descendants through One person. It was not to the “seeds” of Abram but to the “Seed” of Abraham. That Seed is Jesus Christ.
9 Jesus said to him, “Today salvation has come to this house, because this man, too, is a son of Abraham. 10 For the Son of Man came to seek and to save the lost.” — Luke 19:9,10 NIV
16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. 17 For God did not send his Son into the world to condemn the world, but to save the world through him. — John 3:16, 17 NIV