But it is not that the word of God has taken no effect. For they are not all Israel who are of Israel, 7 nor are they all children because they are the seed of Abraham; but, “In Isaac your seed shall be called.” 8 That is, those who are the children of the flesh, these are not the children of God; but the children of the promise are counted as the seed. 9 For this is the word of promise: “At this time I will come and Sarah shall have a son.”
10 And not only this, but when Rebecca also had conceived by one man, even by our father Isaac 11 (for the children not yet being born, nor having done any good or evil, that the purpose of God according to election might stand, not of works but of Him who calls), 12 it was said to her, “The older shall serve the younger.” 13 As it is written, “Jacob I have loved, but Esau I have hated.” — Romans 9:6-13.
But God’s Word, His holy Scripture, is thereby fulfilled. Israel is not simply a physical nation of those descended biologically from Jacob. The promise was not only to the seed of Abraham but to the seed of Isaac, Jacob’s father. Those who are their children are children of the promise. Today, those who come to faith in God through Christ are the spiritual children of the promise. [The Bible Panorama.]