Isaiah 40:4

“Every valley shall be exalted, and every mountain and hill shall be made low, &c.] Which is not to be understood literally, but, as Kimchi says, parabolically and mystically: the meaning is, that in consequence of John’s ministry, and our Lord’s coming, such who were depressed and bowed down with the guilt of sin, and were low and humble in their own eyes, should be raised up and comforted; and that such who were elated with themselves, and their own righteousness, should be humbled; their pride and haughtiness should be brought down, and they treated with neglect and contempt, while great notice was taken of lowly minded ones; (see <421411>Luke 14:11) and (<421814>Luke 18:14): and the…”

“Eastern monarchs send heralds before them in a journey to clear away obstacles, make causeways over valleys, and level hills. So John's duty was to bring back the people to obedience to the law and to remove all self-confidence, pride in national privileges, hypocrisy, and irreligion, so that they should be ready for His coming (Mal 4:6; Luk 1:17). crooked--declivities.”

“Every valley shall be exalted - That is, every valley, or low piece of ground, shall be filled up so as to make a level highway, as was done in order to facilitate the march of armies. This verse is evidently designed to explain what is intended in Isaiah 40:3, by preparing the way for Yahweh. Applied to the return of the Jews from Babylon, it means simply that the impassable valleys were to be filled up so as to make a level road for their journey. If applied to the work of John, the forerunner of the Messiah, it means that the nation was to be called on to put itself in a state of preparation for his coming, and for the success of his labors among them. Vitringa, and others, have…”

“valley: Isa 42:11, Isa 42:15, Isa 42:16; Sa1 2:8; Psa 113:7, Psa 113:8; Eze 17:24, Eze 21:26; Luk 1:52, Luk 1:53; Luk 3:5, Luk 18:14 every mountain: Isa 2:12-15; Job 40:11-13 and the: Isa 42:16, Isa 45:2; Pro 2:15 straight: or, a straight place plain: or, a plain place Isaiah 40:5”

“The summons proceeds in a commanding tone. "Let every valley be exalted, and every mountain and hill made low; and let the rugged be made a plain, and the ledges of rocks a valley." והיה, which takes its tone from the two jussive verbs, is also itself equivalent to ויהי. Instead of גּיא (from גּיא), the pointing in Zac 14:4, we have here (according to Kimchi) the vowel-pointing גּיא; at the same time, the editions of Brescia, Pesaro, Venice 1678, have גּיא (with tzere), and this is also the reading of a codex of Luzzatto without Masoretic notes. The command, according to its spiritual interpretation, points to the encouragement of those that are cast down, the humiliation of the…”