This gospel that we proclaim, that we embrace, and that is central to all things Christian was promised by God to His people through His prophets. This promised gospel has Jesus Christ as the central figure: this person who is fully man (born of the seed of David according to the flesh) and fully God (declared to be the Son of God by the resurrection from the dead). You can listen here to this sermon from New Covenant Reformed Church or the sermon archive page for everything associated with the Epistle to the Romans.
Paul, a bondservant of Jesus Christ, called to be an apostle, separated to the gospel of God 2 which He promised before through His prophets in the Holy Scriptures, 3 concerning His Son Jesus Christ our Lord, who was born of the seed of David according to the flesh, 4 and declared to be the Son of God with power according to the Spirit of holiness, by the resurrection from the dead. 5 Through Him we have received grace and apostleship for obedience to the faith among all nations for His name, 6 among whom you also are the called of Jesus Christ;
7 To all who are in Rome, beloved of God, called to be saints:
Grace to you and peace from God our Father and the Lord Jesus Christ.
8 First, I thank my God through Jesus Christ for you all, that your faith is spoken of throughout the whole world. 9 For God is my witness, whom I serve with my spirit in the gospel of His Son, that without ceasing I make mention of you always in my prayers, 10 making request if, by some means, now at last I may find a way in the will of God to come to you. 11 For I long to see you, that I may impart to you some spiritual gift, so that you may be established—12 that is, that I may be encouraged together with you by the mutual faith both of you and me.
13 Now I do not want you to be unaware, brethren, that I often planned to come to you (but was hindered until now), that I might have some fruit among you also, just as among the other Gentiles. 14 I am a debtor both to Greeks and to barbarians, both to wise and to unwise. 15 So, as much as is in me, I am ready to preach the gospel to you who are in Rome also.16 For I am not ashamed of the gospel of Christ, for it is the power of God to salvation for everyone who believes, for the Jew first and also for the Greek. 17 For in it the righteousness of God is revealed from faith to faith; as it is written, “The just shall live by faith.”