The scriptures tells us that the gospel is to the Jew first and also to the Greek.
The words, to the Jew first, is not a reference to importance but rather of sequence, as Paul declares in Acts 13:46, “It was necessary that the Word of God should FIRST have been spoken to you…”
In Acts 28 we read the following:
23 And when they had appointed him a day, there came many to him into his lodging; to whom he expounded and testified the kingdom of God, persuading them concerning Jesus, both out of the law of Moses, and out of the prophets, from morning till evening.
24 And SOME BELIEVED the things which were spoken, and SOME BELIEVED NOT.
25 And when they agreed not among themselves, they departed, after that Paul had spoken one word, Well spake the Holy Ghost by Esaias the prophet unto our fathers,
26 Saying, Go unto this people, and say, Hearing ye shall hear, and shall not understand; and seeing ye shall see, and not perceive:
27 For THE HEART OF THIS PEOPLE IS WAXED GROSS, and THEIR EARS ARE DULL OF HEARING, and THEIR EYES THEY HAVE CLOSED; lest they should see with their eyes, and hear with their ears, and understand with their heart, and should be converted, and I should heal them.
28 Be it known therefore unto you, that the salvation of God is sent unto the Gentiles, and that THEY WILL HEAR IT.
Paul is quoting from Isaiah 6:9-10, a passage which Jesus also quoted as the reason why he spoke in parables.
13 Therefore speak I to them in parables: BECAUSE THEY SEEING SEE NOT; AND HEARING THEY HEAR NOT, neither do they understand.
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. ~ Matthew 13:13-15
In John 9:35-41 Jesus heard that the man born blind, whom he had healed, had been cast out of the synagogue by the religious leaders.
When Jesus found him he said unto him: “Dost thou believe on the Son of God”? The man answered and said, “Who is he, Lord, that I might believe on him”? Then Jesus said unto him, “You have both seen him, and it is He that talks with you.” The man then said: “Lord, I believe.” And he worshiped Jesus.
Then Jesus said, For JUDGMENT I am come into this world, that they which see not might see; and that they which see might be made blind.
Some of the Pharisees which heard these words asked, “Are we blind also?”
Jesus then said to them, “If ye were blind, ye should have no sin: but now ye say, ‘WE SEE;’ therefore YOUR SIN REMAINETH.”
Notice, in this text above, Jesus says, for judgment, I have come into the world and specifically that judgment includes blinding those who claim to see yet cling to their sin.
John tells us the following in chapter 12:
37 But though he had done so many miracles before them, YET THEY BELIEVED NOT ON HIM:
38 That the saying of Esaias the prophet MIGHT BE FULFILLED, which he spake, Lord, who hath believed our report? and TO WHOM hath the arm of the Lord been revealed?
39 THEREFORE THEY COULD NOT BELIEVE, because that Esaias said again,
40 HE HATH BLINDED THEIR EYES, AND HARDENED THEIR HEART; that they should not see with their eyes, nor understand with their heart, and be converted, and I should heal them.
41 These things said Esaias, WHEN HE SAW HIS GLORY, AND SPAKE OF HIM. ~ John 12:37-41
Through Jesus, God blinded them, hardening them in their disobedience by their refusal to believe in the Son of God. This fulfilled the words of Isaiah and Paul quotes this also in Romans 10 showing how they rejected the gospel which God set before them.
16 But they have not all OBEYED THE GOSPEL. For Esaias saith, LORD, WHO HATH BELIEVED OUR REPORT?
17 So then faith cometh by hearing, and hearing by the word of God.
18 But I say, HAVE THEY NOT HEARD? Yes verily, THEIR SOUND went into all the earth, and THEIR WORDS unto the ends of the world.
19 But I say, DID NOT ISRAEL KNOW ? First Moses saith, I will provoke you to jealousy by them that are no people, and by a foolish nation I will anger you.
20 But Esaias is very bold, and saith, I was found of them that sought me not; I was made manifest unto them that asked not after me.
21 But to Israel he saith, All day long I have stretched forth my hands unto A DISOBEDIENT AND GAINSAYING PEOPLE.
The Gospel is their own message: their words and their sound, as Paul says above in Romans 10, but they were disobedient and rejected it.
It is through this gospel that Israel – not the remnant – but, the rest, as Paul says in Romans 11, were hardened. They only way they will be saved is if they no longer abide in unbelief and obey the gospel.
In Acts 3:24 Peter told them: Yea, and all the prophets from Samuel and those that follow after, as many as have spoken, have likewise foretold of THESE DAYS.
In Acts 13:40 – 41, Paul preached to the Jews and said: Beware therefore, lest that come upon you, which is spoken of in the prophets; Behold, ye despisers, and wonder, and perish: for I work a work IN YOUR DAYS, a work which ye shall in no wise believe, though a man declare it unto you.
Jesus is the stone which the builders rejected, as foretold in their scripture. He is a rock of offence and a stone of stumbling to those who are disobedient to God’s Word of God.
6 Wherefore also it is contained in the scripture, Behold, I lay in Sion a chief corner stone, elect, precious: and he that believeth on him shall not be confounded.
7 Unto you therefore which believe he is precious: but unto them which be DISOBEDIENT, the stone which the builders disallowed, the same is made the head of the corner,
8 And STONE OF STUMBLING, and A ROCK OF OFFENCE, even to them which STUMBLE AT THE WORD, BEING DISOBEDIENT: WHERE UNTO ALSO THEY WERE APPOINTED. ~ 1 Peter 2:6-8
The Gospel is not only salvation to the obedient and believing, it is judgment to the disobedient and unbelieving.