'Olive tree' in the Bible

But if some of the branches have been broken off, and thou though a wild olive hast been grafted in among them, and become a partaker of the root and fatness of the olive tree;

For if thou hast been cut out of the naturally wild olive, and contrary to nature hast been grafted into the good olive: how much more shall these, which are native branches, be grafted into their own olive tree?