Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places smooth:
All Commentaries on Isaiah 40:4 Go To Isaiah 40
Ephrem The Syrian
AD 373
It is said that the valleys are filled, because the Lord has entered the world, and has redeemed all the peoples from the bondage of the devil, and brought them back to the faith and adoration of their Creator and has taught them to hope in eternal salvation. This is also said, because he has filled the deep valleys and the horrible and inhospitable caves with ascetics, who, after abandoning the cares of this world, exclusively devote themselves to honor and praise God.