“Far from it! Rather, God must prove to be true, though every person be found a liar, as it is written: ‘So that You are justified in Your words, and prevail when You are judged’” (Romans 3:4).
Paul is emphatic that the unbelief of some Jews in no way nullifies the faithfulness of God (v.3) to the Abrahamic covenant. Not only is the faithfulness of God not negated by the unfaithfulness of Israel but, God, himself, will provide what is necessary to see the promises of the covenant fulfilled—a faithful Israelite who would accomplish what Israel could not—the One who is Jesus, the Christ. The refusal of some Jews to recognize the promises to Abraham now being fulfilled in Jesus and failing to believe in Him was, for Paul, the equivalent of unfaithfulness to the covenant. As such, the unbelieving Jew shares the same fate as the unbelieving Gentile.