Revelation 1:3 and 22:7, 10, 18-19 make clear that “the prophecy” is the book of Revelation. The spirit—the heart, the focus, the emphasis, the essence—of Revelation is the testimony of Jesus.
This testimony is not only of the Jesus seen clearly in the gospels. It is also the testimony of Jesus living in and through all His believers. The consummation of this corporate testimony of Jesus is New Jerusalem.
John “testified the word of God and the testimony of Jesus Christ, even all that he saw” (Rev. 1:2). All that John saw included New Jerusalem. John paid a price for his seeing.
“I John, your brother and fellow partaker in the tribulation and kingdom and endurance in Jesus, was on the island called Patmos because of the word of God and the testimony of Jesus” (1:9). John was exiled to the Patmos. Because his situation involved tribulation and endurance, he took it “in Jesus,” in the man who suffered and endured in His life on earth.
In this outward suffering John saw four visions “in spirit,” the last of which was New Jerusalem. John wrote not an outward story nor a merely human history. Rather, he presented the testimony of Jesus, including New Jerusalem, seen “in spirit.” We too need to be In Spirit to See and Enter New Jerusalem.
The spirit, the focus, of Revelation is the testimony of Jesus. This includes the seven churches (Rev. ch. 2–3), the multitude (ch. 7), the bright woman (ch. 12), the firstfruits (ch. 14), the overcomers (ch. 15, 20), the bride (ch. 19), and New Jerusalem (ch. 21–22). These should be our focus in Revelation, and like John, we should be in spirit.
See New Jerusalem with a Spirit of Faith.