But it is not as though the word of God has failed. For not all who are descended from Israel belong to Israel, and not all are children of Abraham because they are his offspring, but “Through Isaac shall your offspring be named.” This means that it is not the children of the flesh who are the children of God, but the children of the promise are counted as offspring. For this is what the promise said: “About this time next year I will return, and Sarah shall have a son.”
Romans 9:6-9
Now that Paul has expressed his broken heart and listed many of the privileges God has given His chosen people. He now addresses a question that will influence what he says in the next three chapters of Romans. If God gave to Israel all of those covenants and promises and privileges, what happens to His relationship with Israel now that they have rejected His Son?
In defending the character of God, Paul states that God’s Word has not failed. He will still keep His promises to Israel. God does not go back on His word. Then Paul begins to make a distinction between the physical descendants of Israel and the “true Israel.” This is a recap of Romans 2:28–29, where he says, “For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical. But a Jew is one inwardly, and circumcision is a matter of the heart, by the Spirit, not by the letter.”
Now, Paul begins to give examples from Israel’s history to clarify his point. To begin with, not all of Abraham’s offspring were counted as the “children of Abraham.” Some of them were not included in God’s promises to Abraham’s descendants. Both Abraham’s son Ishmael, born before Isaac (Genesis 16), and his sons with Keturah, born long after Isaac (Genesis 25:1–4), were excluded from Israel.
Paul quotes from Genesis 21:12, where God said to Abraham that it is through Isaac that his offspring will be named. Jesus made similar remarks to His critics, as recorded in the gospel of John (John 8:36–39).
No Israelite would have disagreed with Paul’s example in the previous verse. He pointed out that not all of Abraham’s children were included in the line of God’s promises to Israel. Only those who came through Isaac were included. So, while the promise was certainly given to Abraham’s offspring, it was not promised to absolutely all his descendants.
Now, though, Paul gets to the point of his illustration: It’s not enough to simply be born “of the flesh” into Israel. It is the children of the promise who count as offspring. They are the ones who are truly Israel and will inherit God’s promises to Abraham, Isaac, and Jacob. Paul will build from this argument to describe the difference between these two groups.
Paul is pulling examples from Israel’s history to show what distinguished a “true” Israelite from one who was merely born into the nation. He wants to show, in the end, that God will keep His promises to Israel through those who are truly children of the promise. Mere biology is not the key; what ultimately matters is whether or not a person has the right relationship with God. Paul will use this line of thought to explain why Gentiles, and not only Jews, can be part of God’s plan of salvation.