40:1 Comfort ye. This verse begins the second part of Isaiah’s prophecy. By a remarkable providential arrangement, it is noteworthy that the two divisions of Isaiah (chapters 1–39 and 40–66) contain thirty-nine and twenty-seven chapters, respectively, providentially corresponding to the thirty-nine canonical books of the Old Testament and the twenty-seven books of the New Testament. Appropriately, Part I emphasizes law and judgment, while Part II stresses grace and salvation, as centered in the promised Messiah. The “New Testament” portion of Isaiah begins with the ministry of John the Baptist (Isaiah 40:1-5) and ends with the “new heavens and a new earth” (Isaiah 65:17–66:24), along with the unquenchable fire that awaits the ungodly (Isaiah 66:24). It is also noteworthy that Isaiah 53, the greatest gospel chapter in the Bible, is the central chapter of the New Testament section of the book. And since this fifty-third chapter should really have been selected to begin with Isaiah 52:13, the central verse of this central chapter is Isaiah 53:5: “But He was wounded for our transgressions, He was bruised for our iniquities: the chastisement of our peace was upon Him; and with His stripes we are healed.”
40:3 voice of him. This prophecy was fulfilled seven hundred years later when John the Baptist came to “prepare the way” for Christ (Matthew 3:1-3).
40:4 rough places plain. A remarkable change in the very shape of the earth’s surface will take place during the tribulation, preparing the earth for the glorious kingdom age. The terrible earthquakes (among other geophysical catastrophes that are coming) will destroy the great mountain masses of the world (e.g., Revelation 16:20) and fill up the ocean deeps, smoothing out the topography so that the earth’s lands will all be pleasantly inhabitable, as in the beginning.
40:5 shall be revealed. When the earth’s surface is prepared, and the sinners consumed out of it, then the Lord Jesus will be revealed in all His “power and great glory” (Matthew 24:30).