All the Prophets, with one voice, proclaimed the coming Saviour; but John the Baptist was eminently pointed out as the immediate herald and harbinger of our Lord; Matthew 3:1-3; Malachi 3:1. If the passage be read, as undoubtedly it should be read, spiritually, the humbling principles of grace, in preparing for the cordial reception of the Saviour, will fully explain the lowering of mountains, and making straight the crooked. And how is the glory of Christ revealed, in accomplishing those things in the hearts of his people? Precious Jesus! let every thought be brought low, that thou, and thou alone, mayest be exalted! 2 Corinthians 10:5.
Related Commentaries of Isaiah 40:3
Isaiah 40:3-5
3 The voice of him that crieth in the wilderness, Prepare ye the way of the LORD, make straight in the desert a highway for our God.
4 Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight,b and the rough places plain:
5 And the glory of the LORD shall be revealed, and all flesh shall see it together: for the mouth of the LORD hath spoken it.