But it is not that the word of God has taken no effect. For they are not all Israel who are of Israel, nor are they all children because they are the seed of Abraham; but, “In Isaac your seed shall be called.” 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. For this is the word of promise: “At this time I will come and Sarah shall have a son.”
And not only this, but when Rebecca also had conceived by one man, even by our father Isaac (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), it was said to her, “The older shall serve the younger.” As it is written, “Jacob I have loved, but Esau I have hated.” (Romans 9:6-13)
Usually, we don’t look at sections from Romans quite this big in one article, but I think it’s important to keep this passage together so we can follow Paul’s reasoning.
In Romans 9:1-5, Paul expressed his deep sorrow for the nation of Israel. He goes on to explain why that is in this passage.
Not every Israelite was “of Israel.”
Despite the tremendous blessings God had given to the nation of Israel, not every physical descendant of Abraham, Isaac, and Jacob were part of the “people of God” - “spiritual” Israel.
Just because someone was a physical descendant of Abraham did not mean that God was their father - as Jesus pointed out to the Pharisees (John 8:32-44).
In Romans 2, [Paul] made a similar argument: The real Jew cannot be determined by outward appearances such as physical circumcision, but rather by an inward, spiritual circumcision of the heart (2:28-29). Simply put, spiritual Israel is different from physical Israel, and the Jews had seriously misunderstood their identity by equating “their national heritage with their spiritual standing before God.” - Pollard, Truth for Today Commentary, 327
However, the fact that many Jews were not saved did not mean that God’s word had failed. The failure was not with God but those who rejected the promised Messiah and His gracious gospel.
We must insist with Paul that the real heirs are faithful physical Jews. The blessings offered to all the physical Jews are to be appropriated by faith. Those who were intended to inherit the promises were believing Israelites. - McGuiggan, Romans, 278
But wasn’t God “unjust” for “pulling the rug” out from under the Jews like that? What Paul would show his Jewish readers was that they had completely misunderstood the promises of God.
Paul used two examples from Israel’s past to support his argument about the “selective character of God’s grace” (Pollard, Truth for Today Commentary, 327).
The Example of Isaac.
The Jews were not the only physical descendants of Abraham. But God chose Isaac to be the promised “seed” of Abraham.
Although Ishmael was born before Isaac, Ishmael was never viewed as Abraham’s heir at any time by God (Genesis 22:12).
Isaac was born to Abraham and Sarah after they were both too old to have children - he was the child of promise, a gracious gift by God to Abraham. This promise by God was made to Abraham before Abraham had any children (Genesis 15:1ff).
When God restricted the promise to the seed of Isaac this in no way made God inconsistent with regard to the promise given to Abraham. - Wacaster, Studies in Romans, 334
The Example of Jacob.
God chose Jacob, even though Esau was the firstborn twin! This wasn’t based on anything they had done because God made this choice before the boys were born.
The children were not yet born and so had done neither good nor evil “that the purpose of God might stand.” What “purpose?” His “electing” purpose. Read it for yourself! He wanted to cut away the ground of anyone who claimed that his relationship with God was somehow based on earning or law-keeping. - McGuiggan, Romans, 281
God’s choice of Jacob over Esau did not automatically determine Jacob would be saved and go to Heaven, while Esau would be lost and go to Hell. Genesis 25:21-23 makes it clear that while God’s choice of Jacob over Esau involved two individuals, it regards them as representatives of peoples or nations.
God was not unjust to make a distinction between physical Jews and “spiritual Jews.”
To prove that point, Paul pointed back to when God distinguished between Abraham’s sons and Isaac’s sons.
It is this kind of activity by God that justifies his making the point that it wouldn’t be surprising that He would make a distinction between Jew and Jew. In all the choices made, which Paul mentions, grace and faith are in view and flesh and “Law” are excluded. Flesh and Law were the very bases the Jews were claiming on which they should have been blessed. - McGuiggan, Romans, 283
Not all physical Jews were really God’s people - and that was a shocking teaching to most Jewish people Paul taught.
Next, Paul would answer the question, “Is God unjust for making this distinction between physical Israel and spiritual Israel?”
This is good; we have to know how to distinguish between the spirit and the natural.
If we know God is all-knowing, then God would have known how Jacob and Esau’s life played out. God changed Jacob’s name to Yasharel (Israel in our English transliteration) which means “wrestle with God”. See Genesis 32:22-32 for this account. He knew that Esau would sell his birthright for a meal. Jacob was an overcomer, but Esau was weak. That is the story of mankind right there. Are we to be Overcomers, or the overcome? Overcoming Satan will require a wrestle on our part. Look for no human to do this for you.