What does Romans 1:2 mean?

Paul has identified himself as both a servant and authorized representative of Jesus set apart for the gospel of God. Now he begins to explain, in the middle of his introduction, what the gospel of God is.

First, Paul writes, the gospel of God is not a new thing that has popped up since Jesus' death and resurrection. Instead, the gospel had been promised by God long ago through what his prophets wrote in the "holy Scriptures." Paul's readers would have understood the holy Scriptures to include the books we refer to as the Old Testament.

Paul does not give examples of the promise of the gospel in this brief verse, but he is consistent throughout his writing in insisting that the Scriptures were always pointing forward to the coming of the Messiah and salvation through Him for both Jewish people and Gentiles (Galatians 3:7–9). New Testament books such as Hebrews go to great lengths showing how the Scriptures of the Old Testament were filled with predictions and descriptions of Jesus Christ.