"I ask then, did God reject his people? May it never be! For I also am an Israelite, a descendant of Abraham, of the tribe of Benjamin." "God didn't reject his people, whom he foreknew." Elijah thought he alone was left, but God had reserved for himself seven thousand. "Even so too at this present time also there is a remnant according to the election of grace." If it is by grace, it is no longer of works; otherwise grace is no longer grace.
Paul asks, "did they stumble that they might fall? May it never be!" Through this, salvation has come to the Gentiles. Paul magnifies his ministry, hoping that some of his own people may be saved. If the root is holy, so are the branches.
If some branches were broken off, and a wild olive was grafted in among them to share in the root and richness of the olive tree, it must not boast over the branches. "But if you boast, remember that it is not you who support the root, but the root supports you." Paul warns them not to be conceited, but to fear. He points to the goodness and severity of God. God is able to graft the natural branches in again.
Paul does not want believers to be wise in their own conceits. A partial hardening has come until the fullness of the Gentiles comes in, "and so all Israel will be saved." "For the gifts and the calling of God are irrevocable." "For God has bound all to disobedience, that he might have mercy on all." "Oh the depth of the riches both of the wisdom and the knowledge of God! How unsearchable are his judgments, and his ways past tracing out!" "For of him and through him and to him are all things. To him be the glory for ever! Amen."