I was listening to Romans tonight and something hit me for the first time in chapter 15. I had read the verse and yet missed it. (Aside: eyes are far more deceitful than ears.)
For I tell you that Christ became a servant to the circumcised to show God’s truthfulness, in order to confirm the promises given to the patriarchs, and in order that the Gentiles might glorify God for his mercy. As it is written,
“Therefore I will praise you among the Gentiles,
and sing to your name.”
And again it is said,
“Rejoice, O Gentiles, with his people.”
“Praise the Lord, all you Gentiles,
and let all the peoples extol him.”
And again Isaiah says,
“The root of Jesse will come,
even he who arises to rule the Gentiles;
in him will the Gentiles hope.”
Notice how this goes back to God’s righteousness in chapter 3:
Then what advantage has the Jew? Or what is the value of circumcision? Much in every way. To begin with, the Jews were entrusted with the oracles of God. What if some were unfaithful? Does their faithlessness nullify the faithfulness of God? By no means! Let God be true though every one were a liar, as it is written,
“That you may be justified in your words,
and prevail when you are judged.”
But if our unrighteousness serves to show the righteousness of God, what shall we say? That God is unrighteous to inflict wrath on us? (I speak in a human way.) By no means! For then how could God judge the world? But if through my lie God’s truth abounds to his glory, why am I still being condemned as a sinner? And why not do evil that good may come?—as some people slanderously charge us with saying. Their condemnation is just.
So Paul confirms my reading of this passage in chapter 3, and my thesis about Romans in general: Israel’s unfaithfulness in crucifying the Messiah demonstrated God’s faithfulness and righteousness in accomplishing salvation for the nations in the Messiah. God’s truthfulness is proven.
And furthermore, this goes all the way back to how Paul describes his Gospel at the beginning of Romans, as that which “confirm[s] the promises given to the patriarchs”
Paul, a servant of Christ Jesus, called to be an apostle, set apart for the gospel of God, which he promised beforehand through his prophets in the holy Scriptures, concerning his Son, who was descended from David according to the flesh and was declared to be the Son of God in power according to the Spirit of holiness by his resurrection from the dead, Jesus Christ our Lord
No wonder then, that the Gospel declares God’s righteousness (Romans 1.17). He has kept his promises. He had been true to his word. He had brought salvation to the nations.