Romans 9:7-13

Physical descent from Abraham doesn’t guarantee the inheritance, because God has said: “Through Isaac your descendants will be counted as part of your lineage.” This confirms that it is not merely the natural offspring of Abraham who are considered the children of God; rather, the children born because of God’s promise are counted as descendants. For God promised Abraham: “Now is the time! For in nine months your wife, Sarah, will have a son!” Now, this son was our ancestor, Isaac, who, with his wife, Rebekah, conceived twins. And before her twin sons were born, God spoke to Rebekah and said: “The oldest will serve the youngest.” God spoke these words before the sons had done anything good or bad, which proves that God calls people not on the basis of their good or bad works, but according to his divine purpose. For in the words of Scripture