When Jesus set out to teach, by and large, He had only one subject, The Kingdom. His students, the disciples, therefore were disciples of Jesus, and hence disciples of His Kingdom. There is no teaching that Jesus gave that was not primarily about the Kingdom, even as Matthew 6:33 says, seek first the Kingdom.
When we look at the Gospels, that it was the Gospel of the Kingdom that was to be preached, all the way through Acts 28 where Paul is still preaching the Gospel of the Kingdom under house guard, and beyond, we realize there is no Gospel without the Kingdom.
How did Jesus introduce His parables? What is the Kingdom of God like? That’s it. And, when Jesus gave His famous sermon in Matthew 5-7, who was He teaching? The disciples of that Kingdom.
Any attempt to separate the Gospel of the Kingdom, that is, Christ as the only salvation, from the Kingdom itself, that which was the basis of the power and authority of that Kingdom, we are departing from the fullness of what Jesus brought.
Indeed, as we look through the whole of the Gospel accounts, to overlook the invisible yet potent Kingdom that was in Jesus’ midst os to miss the bulk of what He brought.
The only Gospel there is is the Gospel of the Kingdom, and, as Jesus said, there are few who find it.
Further, we see that it is the Gospel of the Kingdom that was continued to be preached. Matthew 24:14 indicates that it was the “Gospel of the Kingdom” that was preached by the disciples after the crucifixion. In addition, this is also what Paul continued to preach, all the way through the book of Acts to the very last verse.
He proclaimed the kingdom of God and taught about the Lord Jesus Christ—with all boldness and without hindrance!
Acts 28:18
Finally, we see that it was the teachings of Jesus which were constituted the message. As Paul instructed Timothy,
If anyone advocates a different doctrine and does not agree with sound words, those of our Lord Jesus Christ, and with the doctrine conforming to godliness, he is conceited and understands nothing; but he has a morbid interest in controversial questions and disputes about words, out of which arise envy, strife, abusive language, evil suspicions, and constant friction between men of depraved mind and deprived of the truth, who suppose that godliness is a means of gain.
1 Timothy 6:3-5
Contrary to much dispensationalist thought, the words in Red in the Gospels are the New Testament charter. The church is the body of the Kingdom, and anyone who advocates a different “understands nothing”, according to Paul.
The Gospel of the Kingdom is the Gospel of Salvation, but brings men beyond just “inside the door” to the whole house of God (Numbers 12:7). This Gospel of the Kingdom is the fullness of Jesus brought, and includes the demonstrations of power at its preaching and the continued working of God in our midst, but most of all brings us to the life of the Spirit, the enjoyment of the things of God, and the freedom from sin and the desires of the flesh. While in this world, we will have tribulations, we can rejoice, for greater is He that is in us than He that is in the world!