A Few Excerpts Concerning Isaiah

RIDDERBOS: Among the Jews living at the time of Jesus,the picture of the messenger of peace in Isaiah remained alive. The mebasser will come, the messianic time will start. It is not always said who this messenger is. But with his coming the malkuth shalmaim (the kingdom of heaven) will begin.
Thus the roots of Jesus' use of the word "gospel" are discovered. Even if the Rabbinical places were to be eliminated, it would still be evident that Jesus identifies himself with the messenger of joy of Isaiah. For the above mentioned words: "the poor have the good news preached to them" are not only a quotation from Isaiah 61:1, but also in his initial proclomation of the gospel, according to Luke, Jesus explicitly states that the prophecy of the messenger of joy of Isaiah 61 is fulfilled now while he is addressing his hearers. This messenger has been annointed with the Holy Spirit, and has been sent to preach the gospel to the poor (Luke 4:21). Against this Old Testament back ground we should interpret the original meaning of the expression "the gospel of the kingdom of heaven." And it follows that in this preaching of the gospel as it echoes in the ears of Jesus' audience, the kingdom of heaven has become a present reality: the mebasser, the bringer of the good news to the poor, has appeared; the great moment of salvation has begun (p.72).
Ridderbos, Herman. "The Coming of the Kingdom" P&R publishing, 1962.