Romans 1:2

Which he promised afore through his prophets in the holy Scriptures.

This verse seals the identity of the Christian religion with that divine institution set forth prophetically and typically in the Old Testament. The redemptive gospel Paul preached was the very same system proclaimed and partially unfolded in the Old Testament. The identity and character of the Messiah, the nature of his kingdom, and the ultimate replacement of the old covenant with a new (Jeremiah 31:31-35) - all of these things, and many others, are contained in the Old Testament. By so bold a claim, Paul at once established the principle that any believer of the Old Testament should likewise be a believer of the New Testament; for they surely answer, each to the other, as type and antitype, prophecy and fulfillment.

Through his prophets ... Here is a distinction one meets constantly in the Bible, that the words therein contained are not the words of the prophets, but the word of God delivered "through his prophets" (as here), and "through the apostles" (2 Peter 3:2). (See Matthew 1:22; 2:5; 2:15; 2:17; 3:3; 4:14, and throughout the Bible). Paul's summary of the gospel (1 Corinthians 15:3,4) stresses this same point through the recurrence of the phrase, "according to the scriptures." Bruce's definition of the gospel is:

(It is) his joyful proclamation of the victory and exaltation of his Son, and the consequent amnesty and liberation which we may enjoy through faith in him.[5]