Romans 11:17

‘But if some of the branches were broken off, and you, being a wild olive, were grafted in among them, and became partaker with them of the root of the fatness of the olive tree,'

It is in this verse that we first learn that the olive tree is in mind, certainly in so far as Romans 11:17 onwards are in mind. It is difficult, however, to avoid the conclusion from the phrase ‘but if some of the branches were broken off' that these words assume that the branches of the olive tree have already been referred to in some way, i.e. in Romans 11:16 as ‘the root and the branches', especially as Romans 11:18 refers to the root of the olive tree as though it represented the tree, and sees the branches as arising from it. The passage might just, however, be seen as standing apart from Romans 11:16. But, however we see that, the olive tree is certainly in mind from now onwards, and that points to Jeremiah 11:16 where ‘the green olive tree' is specifically the name by which God calls Israel (‘He has called your name “Green Olive Tree”). Compare also Hosea 14:6 and Jewish tradition which both compare Israel to an olive tree. It will be noted in Jeremiah 11:16 that as such it is burned and its branches are broken, a picture indicating the parlous state of Israel at that time. That was, of course, the situation in Jeremiah's day, not necessarily the permanent situation of the olive tree as representing Israel. But it does indicate a tree that was marred.

The point being made here is that branches have been broken off the olive tree, and it is clear from the context (e.g. Romans 11:20) that this refers to unbelieving Israel who have rejected their Messiah. A similar picture is given by Jesus in John 15:1 where ‘abiding in Messiah' is the test, that is hearing Him and responding to Him and His words, whilst those who do not abide are removed and burned. Additionally in Paul's illustration other wild olive branches are engrafted in, who clearly represent Gentile believers. The Gentile believers then commence partaking of the root of the fatness of the olive tree, in other words of all its benefits. They begin to partake of the Messiah, and of the ideal Israel that He represents. They have become a part of Israel, for it must be noted here that these branches now become a part of the olive tree, and thus a part of Israel (however defined). From now on they  ‘are Israel'. Thus Israel now consists of Jews and some Gentiles as indeed it did before, but the difference now is that their faith is in the Messiah rather than in the Law. The olive tree in its entirety continues to be ideal Israel. The broken off branches cease to be a part of Israel. Here the true Israel in God's eyes is seen to be finally composed of the elect, both Jews and Gentiles, as in Romans 9:24.

It should be noted how all this parallels chapter 9, where the chosen remain within the promises of God (Romans 9:7), including later the Gentile believers (Romans 9:24), whilst those who are not chosen are separated off (Ishmael, the sons of Keturah, Esau), whilst in chapter 10 it is by being engrafted into the Messiah that men find salvation, whilst those who do not respond to the Messiah are cut off, they fail to hear the report about the Messiah.

Paul has been criticised for not recognising that it is not sound horticulture to graft wild olive branches into a good olive tree, but in fact it is known that exactly this principle was carried out by certain ancient horticulturalists, the wild olive branches revivifying the olive tree. But that is beside the point, for Paul is using an illustration in order to get over a point, not claiming that it is good horticultural practise in real life.