The Gospel was Promised in the Old Testament Scriptures

Commentary on the Book of Romans

Romans 1:2
… separated to the gospel of God, (vs 1)

vs2 which He promised before through His prophets in the Holy Scriptures,

Gospel means good news. What is the good news from God? It is simply this: that God would make a way to save people from sin and its consequences, and restore what we had lost through disobedience and rebellion towards GOd.
This promised was fulfilled through the death and resurrection of the Son of God, Jesus Christ, in our place. Through the cross all the evil that we deserved came on Jesus, that all the good He deserves might come on us. It works for us when we truly believe in JESUS from the heart. It is not simply believing a doctrine about Jesus that saves us. It is believing in HIM, the Living Word, that brings salvation. This means we must also forsake sin. If we don’t forsake sin, we don’t believe Jesus or take Him seriously. Fair enough?

How had God already promised this gospel? In many ways.

God promised this Gospel way back to Adam and Eve after they had sinned.

Geneis 3:15 And I will put enmity Between you [the snake, the devil] and the woman, And between your seed and her Seed; He shall bruise your head, And you shall bruise His heel.”

God promised that a descendant of the woman would bruise the head of the serpent Satan. This Jesus did. The killing of the first animals to provide coverings for Adam and Eve was also a symbolic picture of the gospel of Jesus Christ. For in the gospel, the Lamb of God that takes away the sin of the world – Jesus – is slain so that his blood might cover our sin and shame.

The gospel is promised in so many other places, but it is usually somewhat obscure. One of the clearer passages in is Isaiah 53.

Isa 53:1 Who has believed our report? And to whom has the arm of the LORD been revealed?
Isa 53:2 For He shall grow up before Him as a tender plant, And as a root out of dry ground. He has no form or comeliness; And when we see Him, There is no beauty that we should desire Him.
Isa 53:3 He is despised and rejected by men, A Man of sorrows and acquainted with grief. And we hid, as it were, our faces from Him; He was despised, and we did not esteem Him.
Isa 53:4 Surely He has borne our griefs And carried our sorrows; Yet we esteemed Him stricken, Smitten by God, and afflicted.
Isa 53:5 But He was wounded for our transgressions, He was bruised for our iniquities; The chastisement for our peace was upon Him, And by His stripes we are healed.
Isa 53:6 All we like sheep have gone astray; We have turned, every one, to his own way; And the LORD has laid on Him the iniquity of us all.
Isa 53:7 He was oppressed and He was afflicted, Yet He opened not His mouth; He was led as a lamb to the slaughter, And as a sheep before its shearers is silent, So He opened not His mouth.
Isa 53:8 He was taken from prison and from judgment, And who will declare His generation? For He was cut off from the land of the living; For the transgressions of My people He was stricken.
Isa 53:9 And they made His grave with the wicked— But with the rich at His death, Because He had done no violence, Nor was any deceit in His mouth.
Isa 53:10 Yet it pleased the LORD to bruise Him; He has put Him to grief. When You make His soul an offering for sin, He shall see His seed, He shall prolong His days, And the pleasure of the LORD shall prosper in His hand.
Isa 53:11 He shall see the labor of His soul, and be satisfied. By His knowledge My righteous Servant shall justify many, For He shall bear their iniquities.
Isa 53:12 Therefore I will divide Him a portion with the great, And He shall divide the spoil with the strong, Because He poured out His soul unto death, And He was numbered with the transgressors, And He bore the sin of many, And made intercession for the transgressors.

There are a lot of other passages in which the gospel is promised. For example here:

Galatians 3:8 And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel to Abraham beforehand, saying, “In you all the nations shall be blessed.”

In Romans, Paul is telling us that God fulfilled his promise to bring good news of salvation through Jesus Christ. Paul was appointed to go with this message in Christ’s name and get people to turn back to God through faith in Jesus Christ.