Isaiah 40:4

4 Each valley shall be enhanced, and each mountain and little hill shall be made low; and shrewd things shall be into straight things, and sharp things shall be into plane ways. (Each valley shall be lifted up, and each mountain and little hill shall be made low; and depraved, or crooked, ways shall be made into straight ways, and sharp places shall be made into smooth places.)

Isaiah 40:4 Meaning and Commentary

Isaiah 40:4

Every valley shall be exalted, and every mountain and hill
shall be made low
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 ( Luke 14:11 ) and ( Luke 18:14 ) : and the crooked shall be straight and the rough places plain;
what before was dark and intricate in prophecy should now become clear; and such doctrines as were not so well understood should now become plain and easy.

Isaiah 40:4 In-Context

2 Speak ye to the heart of Jerusalem, and call ye [to] it, for the malice thereof is [ful]filled, the wickedness thereof is forgiven; it hath received of the hand of the Lord double things for all his sins (it hath received from the hand of the Lord double for all of its sins).

3 The voice of a crier in desert [The voice of the (one) crying in (the) desert], Make ye ready the way of the Lord, make ye rightful the paths of our God in wilderness. (The voice of one crying in the wilderness, Prepare ye the way of the Lord, make ye right the paths in the desert for our God.)

4 Each valley shall be enhanced, and each mountain and little hill shall be made low; and shrewd things shall be into straight things, and sharp things shall be into plane ways. (Each valley shall be lifted up, and each mountain and little hill shall be made low; and depraved, or crooked, ways shall be made into straight ways, and sharp places shall be made into smooth places.)

5 And the glory of the Lord shall be showed, and each man shall see together, that the mouth of the Lord hath spoken. (And the glory of the Lord shall be shown, and all the people shall see it together, that the mouth of the Lord hath spoken it.)

6 The voice of God, saying, Cry thou. And I said, What shall I cry? Each flesh is hay, and all the glory thereof is as the flower of the field. (The voice of God, saying, Cry thou. And I said, What shall I cry? And he saith, Each person is but a blade of grass, and all their life lasteth no longer than a flower in the field.)