Titus 1:2, Rom 16:25, Lk 1:69-70, Mt 1:1, Jn 7:42, 2 Sam 7:12, 2 Tim 2:8, Rev 22:16, Acts 13:33-35, Acts 2:36
The gospel is a promise made in advance through the prophets concerning the Son of God who will do the work of Christ. (Rom 1:2, Titus 1:2, Rom 16:25, Lk 1:69-70)
Rom 1:2 (Which he had promised afore by his prophets in the holy scriptures,)
Titus 1:2 In hope of eternal life, which God, that cannot lie, promised before the world began;
Rom 16:25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began,
Lk 1:69 And hath raised up an horn of salvation for us in the house of his servant David; 70 As he spake by the mouth of his holy prophets, which have been since the world began:
Christ came as a descendant of David. (Rom 1:3, Mt 1:1, Jn 7:42, 2 Sam 7:12, 2 Tim 2:8, Rev 22:16)
Rom 1:3 Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh;
Mt 1:1 The book of the generation of Jesus Christ, the son of David, the son of Abraham.
Jn 7:42 Hath not the scripture said, That Christ cometh of the seed of David, and out of the town of Bethlehem, where David was?
2 Sam 7:12 And when thy days be fulfilled, and thou shalt sleep with thy fathers, I will set up thy seed after thee, which shall proceed out of thy bowels, and I will establish his kingdom.
2 Tim 2:8 Remember that Jesus Christ of the seed of David was raised from the dead according to my gospel:
Rev 22:16 I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, and the bright and morning star.
By resurrecting Jesus, God confirmed to us that Jesus is the Son of God and the Christ. (Rom 1:4, Acts 13:33-35, Acts 2:36)
Rom 1:4 And declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead:
Acts 13:33 God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee. 34 And as concerning that he raised him up from the dead, now no more to return to corruption, he said on this wise, I will give you the sure mercies of David. 35 Wherefore he saith also in another psalm, Thou shalt not suffer thine Holy One to see corruption.
Acts 2:36 Therefore let all the house of Israel know assuredly, that God hath made the same Jesus, whom ye have crucified, both Lord and Christ.
The gospel is that Jesus is the Christ and the Son of God.