What does Romans 9:10 mean?
Paul is building an argument that there exists a difference in Israel: between those who are truly Israelites and will receive the promises of God, versus those who are merely born into the nation. He is pulling examples from Israel's history to make his case. His first example was that not all of Abraham's offspring were included in the line of promise, only Isaac.Now Paul points to Isaac's sons to show that God even picked one twin and not another to receive His covenant promises. Not every single one of Abraham's descendants was made part of the promise of God. There was still an element of God's sovereignty and choice in deciding whom to bless. Paul is emphasizing this point to show that a saving relationship with God is never as simple as merely being born from the right parents.
Isaac's wife Rebekah conceived two children by one man, meaning that she was carrying twins. Only one would carry the promise that was given through Abraham.