The Kingdom of Heaven and the Kingdom of God

Paul's testimony before Festus in Acts 25 where we come to this;

Acts 25:6-12 When Festus had tarried among them more than ten days, he went down to Caesarea; and the next day sitting on the judgment seat commanded Paul to be brought. When he was come, the Jews which came from Jerusalem stood round about, and laid many and grievous complaints against Paul, which they could not prove. While he answered for himself, Neither against the law of the Jews, neither against the temple, nor yet against Caesar, have I offended any thing at all. But Festus, willing to do the Jews a pleasure, answered Paul, and said, Will you go up to Jerusalem, and there be judged of these things before me? To that Paul said, I stand at Caesar's judgment seat, where I ought to be judged: to the Jews have I done no wrong, as you very well know. For if I be an offender, or have committed any thing worthy of death, I refuse not to die: but if there be none of these things whereof these accuse me, no man may deliver me to them. I appeal to Caesar. Then Festus, when he had conferred with the council, answered, You have appealed to Caesar? to Caesar shall you go. 

Next we see that Festus wanting to gain the favor of King Agrippa, brings Paul to him and thereby passes the buck, or in his case the septer over to him. Paul will again rehearse his testimony before King Agrippa.

Acts 26:1-32 Agrippa said to Paul, You are permitted to speak for yourself. Then Paul stretched forth the hand, and answered for himself: I think myself happily, king Agrippa, because I shall answer for myself this day before you touching all the things whereof I am accused of the Jews: Especially because I know you are an expert in all customs and questions which are among the Jews: therefore I beseech you to hear me patiently. My manner of life from my youth, which was at the first among my own nation in Jerusalem, know all the Jews; Who know me from the beginning, if they would testify, that after the most straitest sect of our religion I lived as a Pharisee. And now I stand an am judged for the hope of the promise made of God to our fathers: to which promise our twelve tribes, instantly (with all due diligence) serving God day and night, in the hope to come. For which hope's sake, king Agrippa, I am accused of the Jews. Why should it be thought a thing incredible with you, that God should raise the dead? I verily thought with myself, that I ought to do many things contrary to the name of Jesus of Nazareth. Which things I also did in Jerusalem: and many of the saints did I shut up in prison, having received authority from the chief priests; and when they were put to death, I gave my voice against them. And I punished them oft in every synagogue, and compelled them to blaspheme; and being exceedingly mad against them, I persecuted them even to strange cities.

Paul from here on Proclaims

the Gospel of God's Grace received in and through Christ alone.

Otherwise known by John the Baptist and Jesus as the kingdom of heaven and of God because of the Jewish despensational period and the Abrahamaic Covenant restrictions and limitations (in the Mosaic Law , the Prophets and Psalms) they were under.

Whereupon as I went to Damascus with authority and commission from the chief priests, then at midday, O king, I saw in the way, when a LIGHT from heaven, above the brightness of the sun, shining round about me and them which journeyed with me. And when we were all fallen to the earth, I heard a voice speaking to me, and saying in the Hebrew tongue, Saul, Saul, why persecute you Me? it is hard for thee to kick against the pricks. To which I said, Who are You, LORD? And He said, I am Jesus whom you persecute. But arise, and stand upon your feet: for I have appeared to you for this purpose, to make you a minister and a witness both of these things which you have seen, and of those things in the which I will appear to you; Delivering you from the people, and from the Gentiles, to whom now I send you, to open their eyes, to turn them from darkness to Light, and from the power of Satan to God, that they may receive forgiveness of sins, and inheritance among them which are sanctified by faith that is in Me.

Thereupon, O king Agrippa, I was not disobedient to the heavenly vision: But have showed first to them of Damascus, and at Jerusalem, and throughout all the coasts of Judea, and to the Gentiles, that they should repent and turn to God, and do works meet (showing) for repentance. For these causes (charges) the Jews caught me in the temple, and went about to kill me. Having therefore obtained help of God, I continue to this day, witnessing both to small and great, saying no other things than those which the prophets and Moses did say should come: That Christ should suffer, that He should be the first that should arise from the dead, and should show Light to the people, and to the Gentiles. And as he thus spoke for himself, Festus said with a loud voice, Paul, you are beside yourself; much learning does make you mad.

But Paul said, I am not mad, most noble Festus; but speak the words of truth and soberness. For the king knows of these things, before whom also I speak freely: for I am persuaded that none of these things are hidden from him; for this thing was not done in a corner, but openly. King Agrippa, believe you the prophets? I know that you believe. Then Agrippa said to Paul, Almost you persuade me to be a Christian. And Paul said, I would to God, that not only you, but also all that hear me this day, were both almost, and altogether such as I am, except these bonds.

 

When he had thus spoken, the king rose up, and the governor, and Bernice, and they that sat with them: And when they were gone aside, they talked between themselves, saying, This man does nothing worthy of death or of bonds. Then said Agrippa to Festus, This man might have been set at liberty, if he had not appealed to Caesar. 
 
What is this Gospel which Paul bears witness to?