Adam Clarke on Romans 11:17

And if some of the branches, etc. - If the present nation of the Jews, because of their unbelief, are cut off from the blessings of the Church of God, and the high honor and dignity of being his peculiar people; and thou, being a wild olive - ye Gentiles, being without the knowledge of the true God, and consequently bringing forth no fruits of righteousness, wert grafted in among them - are now inserted in the original stock, having been made partakers of the faith of Abraham, and consequently of his blessings; and enjoy, as the people did who sprang from him, the fatness of the olive tree - the promises made to the patriarchs, and the spiritual privileges of the Jewish Church: -