Paul continues to discuss the position of the Jews in relation to the salvation of God. We see that because of unbelief, they were broken out of the blessings of the relationship promised to Abraham and his descendants. Contrary to nature, God grafted the Gentiles into that relationship through faith - so they became spiritual descendants of Abraham and participants in those blessings. However, there is a warning here that if the Gentiles abandon the faith in Christ that secured those blessings for them, they may once more be broken from the tree. Likewise there is an encouragement that if the Jews turn from their unbelief and embrace Jesus as Messiah and Lord, they can be joined once again to the tree and participate in the blessings that are entailed.