Some Christians attempt to distinguish between a Jewish bride and the church by claiming that Jesus only preached the kingdom message when here on earth, and that Paul actually introduced the Gospel of Grace whereby we in the Church are saved separate from Israel. Let’s review Scripture on this thinking.

Both Matthew 4:23 and

Matthew 9:35 tell us: Jesus was going through all the cities and villages, teaching in their synagogues and proclaiming the gospel of the kingdom, and healing every kind of disease and every kind of sickness.
Luke 4:43 But He said to them, “I must preach the kingdom of God to the other cities also, for I was sent for this purpose.”
Luke 10:8-9 Whatever city you enter and they receive you, eat what is set before you; and heal those in it who are sick, and say to them, ‘The kingdom of God has come near to you.’
Jesus later told these same disciples to
Luke 9:60 But He said to him, “Allow the dead to bury their own dead; but as for you, go and proclaim everywhere the kingdom of God.”
Psalm 45:6 Your throne, O God, is forever and ever; A scepter of uprightness is the scepter of Your kingdom.
Daniel 2:44 In the days of those kings the God of heaven will set up a kingdom which will never be destroyed, and that kingdom will not be left for another people; it will crush and put an end to all these kingdoms, but it will itself endure forever.
The question we must ask is — is this gospel that Jesus spoke just for Israel?
As we continue to look at scripture it will become apparent that The kingdom of God is established first in the hearts of men. It is eternal, and when all have been allowed in then it will be established on earth. But scripture is needed to prove that.
Acts 1:3, 6-7 To these He also presented Himself alive after His suffering, by many convincing proofs, appearing to them over a period of forty days and speaking of the things concerning the kingdom of God. So when they had come together, they were asking Him, saying, “Lord, is it at this time You are restoring the kingdom to Israel?” He said to them, “It is not for you to know times or epochs which the Father has fixed by His own authority;
Matthew 12:28 But if I cast out demons by the Spirit of God, then the kingdom of God has come upon you.
Matthew 19:24 Again I say to you, it is easier for a camel to go through the eye of a needle, than for a rich man to enter the kingdom of God.”
Matthew 21:31 Which of the two did the will of his father?” They *said, “The first.” Jesus *said to them, “Truly I say to you that the tax collectors and prostitutes will get into the kingdom of God before you.
Matthew 21:43-44 Therefore I say to you, the kingdom of God will be taken away from you and given to a people, producing the fruit of it. And he who falls on this stone will be broken to pieces; but on whomever it falls, it will scatter him like dust.”
These verses obviously see the establishment of the kingdom of God through the promised New Covenant which Jesus took from those Jews who were broken off (remember broken off for their unbelief), and then given to other Jews (the Apostles) and to those from all of mankind who would believe their message. Romans 11 tells us these things have happened.
Mark 1:15 and saying, “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.”
The gospel here implies that there is only one. But what of the kingdom?

The kingdom of God is here, but notice not the Messianic kingdom which was promised to Israel and the heirs of Messiah. It is this kingdom for which we pray — thy kingdom come, Thy will be done on earth…
The call here in Mark 1, is for repentance and believing the gospel because the kingdom of God is at hand. So was it really at hand then? Listen:
Acts 19:8-10 And he (paul) entered the synagogue and continued speaking out boldly for three months, reasoning and persuading them about the kingdom of God. But when some were becoming hardened and disobedient, speaking evil of the Way before the people, he withdrew from them and took away the disciples, reasoning daily in the school of Tyrannus. This took place for two years, so that all who lived in Asia heard the word of the Lord, both Jews and Greeks.
Acts 20:25-26 “And now, behold, I know that all of you, among whom I went about preaching the kingdom, will no longer see my face. Therefore, I testify to you this day that I am innocent of the blood of all men.
Acts 28:23 When they had set a day for Paul, they came to him at his lodging in large numbers; and he was explaining to them by solemnly testifying about the kingdom of God and trying to persuade them concerning Jesus, from both the Law of Moses and from the Prophets, from morning until evening.
1 Corinthians 6:9 Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived; neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor homosexuals,
1 Corinthians 15:24 then comes the end, when He hands over the kingdom to the God and Father, when He has abolished all rule and all authority and power.
So these verses prove that the Apostle Paul was preaching this same Kingdom of God gospel that Jesus preached. But this kingdom was already being established in the hearts of men. No fornicator, adulterer or homosexual will see this kingdom, and yet some of us were these very persons. So what happened to us? John says in Jn 1: to as many as believed they were given power to become the sons of God.
John 3:3, 10 Jesus answered and said to him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.” Jesus answered and said to him, “Are you the teacher of Israel and do not understand these things?
Jesus here makes the kingdom the reward of the born again. We have been given the Holy Spirit — the power to become what we are not.
Mark 4:11-12 And He was saying to them, “To you has been given the mystery of the kingdom of God, but those who are outside get everything in parables, so that while seeing, they may see and not perceive, and while hearing, they may hear and not understand, otherwise they might return and be forgiven.”
So why was the kingdom actually hidden from the Jews. I really don’t know the answer to that. Perhaps it was because these Jews had the scriptures that spoke of Him, even referring to the time for His coming, and still they did not seek or recognize Him.
But one thing seems certain; Jesus knew that there was no chance of their accepting Him so long as they remained in their unrepentant degenerate state blinded by their sin.
Salvation is the method for entrance into this kingdom which now exists in the hearts of man. One day it will also be revealed on this earth. The other verses help make it clear that it is here now and visible now through the fruit of the new birth. Jesus made it clear in these verses that men who were alive at that time would see it before they died.
But Jesus also taught us to pray Thy Kingdom come Thy will be done on earth as it is in heaven. The kingdom did come in that day in the hearts of men just as Jesus said, but the end of the prayer has not yet been fulfilled. We now look for the kingdom’s establishment on earth– the millennial kingdom.
Paul preached the gospel of God as did Jesus in Mark 1:14, listen.

Acts 28:28-31 Therefore let it be known to you that this salvation of God has been sent to the Gentiles; they will also listen.” When he had spoken these words, the Jews departed, having a great dispute among themselves. And he stayed two full years in his own rented quarters and was welcoming all who came to him, preaching the kingdom of God and teaching concerning the Lord Jesus Christ with all openness, unhindered.

This is the Apostle Paul preaching the kingdom.
Jesus Mark 1:14-15 Now after John had been taken into custody, Jesus came into Galilee, preaching the gospel of God, and saying, “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.”
These vs’s do not say that the kingdom of God is a different gospel. Paul says there is only one Gospel. Paul reprimanded Peter for disobeying this Gospel: 14 But when I saw that they were not straightforward about the truth of the gospel, I said to Peter before them all, “If you, being a Jew, live in the manner of Gentiles and not as the Jews, why do you compel Gentiles to live as Jews? (Galatians 2:14)

Let me pose this to you– if the kingdom gospel is a separate gospel, why did Paul not tell us about it. Because he did preach the kingdom of God as we see in Acts 28. So there is no question that he knew about the kingdom. So, If there is a separate gospel of the kingdom then Paul totally misled us, by telling us that there is only one gospel. In fact what he says in Acts 28:28 is that this same salvation that was sent for the Jews is also given for the Gentiles. So there is no separate gospel of the kingdom just for the Jews.
Matthew 28:19-20 Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit, teaching them to observe all that I commanded you; and lo, I am with you always, even to the end of the age.”

It is claimed that the kingdom gospel concerns the Kingdom that Jesus the Christ was offering Israel. Why then would they be asked to preach it to all nations? And what is this age that Jesus will see through to the end?