Acts 3:13-15, Mt 13:14-17, Rom 15:21, Rom 16:25-27, 1 Jn 1:1-2
In the Old Testament, Isaiah prophesied that the coming Christ would be bruised and that the nations would later hear and understand the gospel of Christ. (Isa 52:13-15)
Isa 52:13 Behold, my servant shall deal prudently, he shall be exalted and extolled, and be very high. 14 As many were astonied at thee; his visage was so marred more than any man, and his form more than the sons of men: 15 So shall he sprinkle many nations; the kings shall shut their mouths at him: for that which had not been told them shall they see; and that which they had not heard shall they consider.
Jesus, the Christ, was handed over to Pilate to save us, died and rose from the dead three days later. (Acts 3:13-15)
Acts 3:13 The God of Abraham, and of Isaac, and of Jacob, the God of our fathers, hath glorified his Son Jesus; whom ye delivered up, and denied him in the presence of Pilate, when he was determined to let him go. 14 But ye denied the Holy One and the Just, and desired a murderer to be granted unto you; 15 And killed the Prince of life, whom God hath raised from the dead; whereof we are witnesses.
Some of the people of Israel heard and saw the gospel that most of the people of Israel did not understand. (Matthew 13:14-17, Romans 15:21)
Matthew 13:14 And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive: 15 For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes and hear with their ears, and should understand with their heart, and should be converted, and I should heal them. 16 But blessed are your eyes, for they see: and your ears, for they hear. 17 For verily I say unto you, That many prophets and righteous men have desired to see those things which ye see, and have not seen them; and to hear those things which ye hear, and have not heard them.
Romans 15:21 But as it is written, To whom he was not spoken of, they shall see: and they that have not heard shall understand.
The gospel of Christ, hidden from time immemorial, was delivered through the writings of the prophets, and the reality of that gospel was revealed. The gospel is that Jesus is the Christ. (Romans 16:25-27, 1 John 1:1-2)
Romans 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: 27 To God only wise, be glory through Jesus Christ for ever. Amen.
1 John 1:1 That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, of the Word of life; 2 (For the life was manifested, and we have seen it, and bear witness, and shew unto you that eternal life, which was with the Father, and was manifested unto us;)