If we were to look for one single theme that seems to be the most central and most important theme of the entire gospel of Matthew, it would be the theme of the coming of the kingdom. We see in the first instance that the term gospel refers to the gospel of the kingdom — the good news of the announcement of the breakthrough of the kingdom of God. In Matthew’s case, he uses the phrase “kingdom of heaven” rather than the terminology “kingdom of God.” It seems he does this not because he has a different view of the meaning or content of the kingdom of God; rather, out of sensitivity to his Jewish readers, he makes common use of what is called periphrasis, a certain type of circumlocution to avoid mentioning the sacred name of God. So for Matthew, the doctrine of the kingdom of heaven is the same kingdom that the other writers speak of as the kingdom of God.
Matthew talks about the breakthrough of the kingdom and the arrival of Jesus. He announces the coming of the kingdom at the beginning of Jesus’ public ministry, and at the end of the book Matthew speaks about the final consummation of the coming of that kingdom in the Olivet Discourse. So from the first page of Matthew to the last page, we see the unifying theme of the coming of the kingdom of God in the appearance of the king Himself, who is the Messiah of Israel.
Matthew 3:2 and saying, “Repent, for the kingdom of heaven is at hand!”
Mark 1:15 and saying, “The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the gospel.”
In the above two scriptures we see a clear message that the kingdom of heaven and the kingdom of God are the same.
The first scripture is said by John the Baptist and the second by Jesus himself. There can be no reasonable doubt that they are talking about the same thing.
The gospel of Matthew is rich in detailed information about the teaching of Jesus and particularly in His parables, which are not always included in the other gospels. Again, the central focus of the parables of Jesus is the kingdom, where He introduces parables by saying, “The kingdom of heaven is like unto this…” or “the kingdom of heaven is like unto that….” If we are to understand the significance of the appearance of Jesus in the fullness of time to inaugurate the kingdom and the whole meaning of redemptive history, we see that focus come into clear view in the gospel according to Matthew.