Paul’s question presumes our knowledge of his ongoing epistolary argument: “did [Israel] stumble in order that they might fall?” (11:11). Did Israel in fact stumble, and if so how? Indeed, they did; indeed they have, as Paul describes in the ninth chapter, “They have stumbled over the stumbling stone, as it is written, ‘Behold, I am laying in Zion a stone of stumbling, and a rock of offense; and whoever believes in him will not be put to shame” (Rom. 9:32-33). Pursuing the righteousness of God by works not faith, they stumbled over Christ. Or, as Paul puts it in the tenth chapter, “For, being ignorant of the righteousness of God, and seeking to establish their own, they did not submit to God’s righteousness. For Christ is the end of the law for righteousness to everyone who believes” (Rom. 10:3-4).
When Christians realize that their citizenship is in heaven, they begin acting as responsible citizens of earth. They invest wisely in relationships because they know they’re eternal.