1. Paul's sorrow and anguish (1-5).
Israel had received every spiritual blessing imaginable. They had been adopted as sons of God and were the people the Messiah came from. Paul had his broken heart for his people. He loved them so deeply - even wishing that he could be cut off from Christ if it meant their salvation.
2. God's sovereign choice (6-18).
The fault was not with God's word. His promise was good, but it was not for all of Abraham's physical descendants. It was to those who were sovereignly chosen by God. Does it seem unfair? If so, then we need to remember that God does not owe salvation to anyone. Mercy is not something we deserve, but a wonderful gift that God has given to those he has sovereignly chosen. God says, "I will have mercy on whom I have mercy."