“For I say that Christ has become a servant to the circumcision on behalf of the truth of God to confirm the promises given to the fathers, and for the Gentiles to glorify God for His mercy; as it is written, ‘Therefore I will give praise to You among the Gentiles, and I will sing to Your name.’” (Romans 15:8–9, NASB)
Paul’s purpose in writing these verses was to explain why Jews and Gentiles should accept each other into fellowship (cf. v. 7). Huge differences existed between them regarding circumcision, diet, and the observance of days (cf. 14:1–3, 5–6). Despite these distinctions they should accept each other. That is why Paul begins 15:8 with “for.” The Lord’s ministry had both Jews and Gentiles in mind. He became a servant (diakonos) of the circumcision, the mark of the Abrahamic covenant, to confirm the promises made to the Fathers. He did not fulfill all the promises because many are yet to be fulfilled—the land promises to Abraham, Isaac, Jacob, and their seed; an eternal kingdom and king; the national conversion of Israel, etc. These promises, still unfilled, were confirmed by the Lord’s ministry and words. The truth of God is at stake here.
The Lord Jesus also had Gentiles as a target of blessing. God promised Abraham that “all the families of the earth” would be blessed in him (Gen. 12:3; 15:18; cf. Isaac, Gen. 22:18). So it was, Christ’s life and ministry made it possible for Gentiles “to glorify God for His mercy.” “Mercy” in the New Testament is always directed toward misery. The Gentiles apart from Christ are in a sorry state (cf. Eph. 2:11–12). The Lord’s coming, life, and death made it possible to extend forgiveness and promise to Gentiles.
In Romans 15:9–12, Paul quotes four Old Testament passages that predict Gentile blessing in the coming ages.
The first coming of Christ confirmed the future fulfillment of Israel’s promises on behalf of the truth of God. Likewise it made it possible for Gentiles to glorify God for His mercy now, in the age to come, and forever.
Because Christ came, died, and was resurrected, we all should welcome one another in fellowship.