Romans 1:2 :

which he promised before through his prophets in the holy Scriptures,

The good news that Paul is going to talk about here comes as no surprise to those who are aware of the Old Testament. Do you remember what happened in the story of Jesus after he resurrected?

Luke 24:25-27 :

He said to them, “Foolish men, and slow of heart to believe in all that the prophets have spoken! Didn’t the Christ have to suffer these things and to enter into his glory?” Beginning from Moses and from all the prophets, he explained to them in all the Scriptures the things concerning himself.

Jesus Himself, after He had resurrected, explained to the disciples what was said about Him in the Old Testament. Paul highlights many of these passages in this letter, but there are many more.

Before Jesus resurrected he also told the people that the Bible talked about Him.

John 5:37-40 :

“The Father himself, who sent me, has testified about me. You have neither heard his voice at any time, nor seen his form. You don’t have his word living in you; because you don’t believe him whom he sent.

“You search the Scriptures, because you think that in them you have eternal life; and these are they which testify about me. Yet you will not come to me, that you may have life.”

When you become a Christian, the Old Testament really opens up to you. You start to realize, by the power of the Holy Spirit, that God was talking about Jesus over and over again. Yes, we are foolish and blinded in our minds about God because we naturally don’t want to hear what He has to say but it is all there.