The Scofield Bible Commentary, by Cyrus Ingerson Scofield, , at sacred-texts.com
The first two verses of Isaiah 40 (Isa 40:1-2) give the key-note of the second part of the prophecy of Isaiah. The great theme of this section is Jesus Christ in His sufferings, and the glory that shall follow in the Davidic kingdom. (See "Christ in Old Testament," sufferings,) (Gen 4:4); (Heb 10:18) glory, (Sa2 7:8-15); (Zac 12:8) Since Israel is to be regathered, converted, and made the centre of the new social order when the kingdom is set up, this part of Isaiah appropriately contains glowing prophecies concerning these events. The full view of the redemptive sufferings of Christ (for example Isaiah 53) leads to the evangelic strain so prominent in this part of (Isa 55:1-3).
The change in style, about which so much has been said, is no more remarkable than the change of theme. A prophet who was also a patriot would not write of the sins and coming captivity of his people in the same exultant and joyous style which he would use to describe their redemption, blessing, and power. In (Joh 12:37-44) quotations from Isaiah 53 and 6 are both ascribed to Isaiah.
A remarkable reference to the sphericity of the earth. See, also, (Isa 42:5); (Isa 44:24); (Isa 51:13); (Job 9:8); (Psa 104:2); (Jer 10:12).