Here are more topics than one which call for reverent notice and study.
1. The imagery of the Olive, with its root, stem, and branches. The Olive, rich and useful, long-lived, and evergreen, stands, as a "nature-parable" of spiritual life, beside the Vine, the Palm, and the Cedar, in the Garden of God. Sometimes it pictures the individual saint, living and fruitful in union with his Lord (Psal. lii. 8). Sometimes it sets before us the fertile organism of the Church, as here, where the Olive is the great Church Universal in its long life before and after the historical coming of Christ; the life which in a certain sense began with the Call of Abraham, and was only magnificently developed by the Incarnation and Passion. Its Root, in this respect, is the great Father of Faith. Its Stem is the Church of the Old Testament, which coincided, in the matter of external privilege, with the nation of Israel, and to which at least the immense majority of true believers in the elder time belonged. Its Branches (by a slight and easy modification of the image) are its individual members, whether Jewish or Gentile. The Master of the Tree, arriving on the scene in the Gospel age, comes as it were to prune His Olive, and to graft. The Jewish "branch," if he is what he seems, if he believes indeed and not only by hypothesis, abides in the Tree. Otherwise, he is--from the divine point of view--broken off. The Gentile, believing, is grafted in, and becomes a true part of the living organism; as genuinely and vitally one with Abraham in life and blessing as his Hebrew brother. But the fact of the Hebrew "race" in root and stem rules still so far as to make the re-ingrafting of a Hebrew branch, repenting, more "natural" (not more possible, or more beneficial, but more "natural") than the first ingrafting of a Gentile branch. The whole Tree is for ever Abrahamic, Israelite, in stock and growth; though all mankind has place now in its forest of branches.
2. The imagery of Grafting. Here is an instance of partial, while truthful, use of a natural process in Scripture parable. In our gardens and orchards it is the wild stock which receives, in grafting, the "good" branch; a fact which lends itself to many fertile illustrations. Here, on the contrary, the "wild" branch is inserted into the "good" stock. But the olive-yard yields to the Apostle all the imagery he really needs. He has before him, ready to hand, the Tree of the Church; all that he wants is an illustration of communication and union of life by artificial insertion. And this he finds in the olive-dresser's art, which shews him how a vegetable fragment, apart and alien, can by human design be made to grow into the life of the tree, as if a native of the root.
3. The teaching of the passage as to the Place of Israel in the divine Plan of life for the world. We have remarked on this already, but it calls for reiterated notice and recollection. "At sundry times, and in divers manners," and through many and divers races and civilizations, God has dealt with man, and is dealing with him, in the training and development of his life and nature. But in the matter of man's spiritual salvation, in the gift to him, in his Fall, of the life eternal, God has dealt with man, practically, through _one_ race, Israel. Let it never be forgotten that the "sundry times and divers manners" of the apostolic Epistle (Heb. i. 1) are all referred to "the prophets"; they are the "times" and "manners" of the Old Testament revelation. And when at length the same Eternal Voice spoke to man "_in the Son_" (ἐν Ὑιῷ), that Son came of Israel, "took hold of Abraham's seed" (Heb. ii. 16), and Himself bore definite witness that "salvation is from the Jews" (John iv. 24). Amidst the unknown manifoldness of the work of God for man, and in man, this is single and simple--that in one racial line only runs the stream of authentic and supernatural revelation; in the line of this mysteriously chosen Israel. From this point of view, the great Husbandman has planted not a forest but a Tree; and the innumerable trees of the forest can get the sap of Eden only as their branches are grafted by His hand into His one Tree, by the faith which unites them to Him who is the Root below the root, "the Root of David," and of Abraham.