2 Pt 3:2 That ye may be mindful of the words which were spoken before by the holy prophets, and of the commandment of us the apostles of the Lord and Saviour:
This gospel had already foretold through the Old Testament prophets that the Son of God would come to save us. (Rom 1:2, Lk 1:70, Acts 3:20-21, Acts 13:32-33)
Rom 1:2 (Which he had promised afore by his prophets in the holy scriptures,)
Lk 1:70 As he spake by the mouth of his holy prophets, which have been since the world began:
Acts 3:20 And he shall send Jesus Christ, which before was preached unto you: 21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began.
Acts 13:32 And we declare unto you glad tidings, how that the promise which was made unto the fathers, 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.
Christ has come, witnessed by the law and the prophets. That Christ is Jesus. The righteousness of God comes to all who believe in Jesus as the Christ. (Rom 3:21-22, Rom 16:25-26)
Rom 3:21 But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets; 22 Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:
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, 26 But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith: