Delimiting the Text
11 So I ask, did they stumble in order that they might fall? By no means! Rather through their trespass salvation has come to the Gentiles, so as to make Israel jealous.
12 Now if their trespass means riches for the world, and if their failure means riches for the Gentiles, how much more will their full inclusion mean!
13 Now I am speaking to you Gentiles. Inasmuch then as I am an apostle to the Gentiles, I magnify my ministry
14 in order somehow to make my fellow Jews jealous, and thus save some of them.
15 For if their rejection means the reconciliation of the world, what will their acceptance mean but life from the dead?
16 If the dough offered as firstfruits is holy, so is the whole lump, and if the root is holy, so are the branches.
The question that Paul asks in verse 11 is a strange to consider initially. Israel has indeed stumbled and fell, as evidenced by not only the immediately preceding discussion in verses 1-10, but reaching back all the way to Romans 9:30. But he denies that Israel has stumbled and fallen! This question arises directly from his own claim that Israel has stumbled and that only a remnant is saved now (11:5). Looking forward to 11:25 and onwards, the discussion turns to the future salvation of Israel; the issue on Paul’s heart now is whether Israel will be saved in the future, since they are accursed and cut off now. The question then, should be interpreted as whether Israel stumbled with the purpose of falling from grace permanently. The question is not whether Israel merely stumbled and fell, but did they do so finally. And to this, Paul says no – there is still a glorious future for Israel.
He grounds this future by claiming that Israel will become jealous because of the salvation that has contemplated the Gentiles. Israel did not stumble for the purpose of falling, they stumbled for the purpose of salvation for the Gentiles. Verses 11b-12 come in the form of an argument from the lesser to the greater. The implication of their jealousy is their full salvation, as the end of the hypothetical argument of verse 12 suggests. Israel has stumbled for the sake of the salvation of the Gentiles, how much more glorious it will be when the beloved nation of God is saved.
In verses 13-14, Paul reintroduces his personal concern. The purpose of the salvation of Gentiles is to make Israel jealous so that they might be saved. Therefore, as the apostle to the Gentiles, he desires to excel all the more in his ministry so as to incite the saving jealousy in his fellow brothers.
The thought and structure of verse 15 is similar to verse 12, an argument from the lesser to the greater. Israel’s “trespass” in verse 12 is paralleled in Israel’s “rejection”, confirming Paul’s dual arguments that Israel’s rejection of God is congruous with God’s rejection of Israel. However, the result of Israel’s full inclusion in verse 12 is vague, whereas in verse 15 the result of Israel’s salvation is “life from the dead”. Here, Schreiner and Moo are both in agreement that Israel’s salvation will precede the resurrection of the dead, and that their salvation will be the climax of the age. Murray dissents and says that “life from the dead” refers to a new spiritual life in many places where death ruled. Verse 16 however shows that the main thought of this passage is not the specific result of the salvation of all Israel, but the surety of it. Israel is still beloved for the sake of their forefathers, and there remains a future to be fulfilled for them.
There are two metaphors provided in verse 16 that parallel one another – the dough and the lump, and the roots and the branches. The metaphor of the roots and the branches is extended in verses 17-24 so that the native and the grafted branches are both supported by root. The conclusion of verse 28, that Israel is beloved for the sake of their forefathers, indicates that the patriarchs are the referent of the root. Collapsing the parallelism, the dough is an Old Testament illustration (from Numbers 15:17-21) of the patriarchs. Because God has loved the patriarchs and made promises to them, he will save Israel.
 A couple other positions on the referent of the dough/roots are popular here. Some advocate for the dough to be the Jewish remnant, and the lump to be the whole body of believers. This is tempting, because the immediately preceding context speaks of the Jewish remnant. However, the root/branch parallel fails to stand up in light of verse 18, for the Jewish remnant is not the reason that the Gentiles are supported.