The lesson in this passage is an excellent one. Isaiah 40 has several different “voices”. Some are explicitly labeled as voices and some are not. The main point from each voice is easier discerned than exactly who is speaking and to whom they are speaking. The principles behind the speech are much easier to figure out.
Isaiah 40:3-9 states, A voice is calling, "Clear the way for the Lord in the wilderness; Make smooth in the desert a highway for our God.
4 "Let every valley be lifted up, And every mountain and hill be made low; And let the rough ground become a plain, And the rugged terrain a broad valley; 5 Then the glory of the Lord will be revealed, And all flesh will see it together; For the mouth of the Lord has spoken." 6 A voice says, "Call out. "Then he answered, "What shall I call out?" All flesh is grass, and all its loveliness is like the flower of the field. 7 The grass withers, the flower fades, When the breath of the Lord blows upon it; Surely the people are grass. 8 The grass withers, the flower fades, But the word of our God stands forever. 9 Get yourself up on a high mountain, O Zion, bearer of good news, Lift up your voice mightily, O Jerusalem, bearer of good news; Lift it up, do not fear. Say to the cities of Judah, "Here is your God!" (NASU)
The message is that God is coming in splendor to reveal Himself to His creation. In keeping with His majesty, the road will be leveled and smoothed in preparation for His royal procession. God has declared that His glory will be revealed to a watching world. The royal spokesman will point out the massive contrast between the Creator and the creature. The creature and all of creation is just as permanent as grass which is about as impermanent as it gets. Grass only lasts for one summer. It will come up in the spring and die out in the fall of the year. Drought can kill it. Heavy frost can kill it. If it grows tall, a strong wind will lay it down. Grass is the epitome of transience. The flower is even more short lived. The flower blooms and is beautiful for a very short time before it fades. Often it does not even last long enough to fade. A moderate wind may very well disconnect it from the stem. A hard rain may knock it to the ground. A light frost may cause the flower to fall. The grass and the flower combine to paint a powerful picture of the temporary earthly existence of mankind.
In contrast, the word of God stands forever. If even the word of God is eternal, then certainly we can take courage and comfort in the eternal nature of God Himself. Surely, this is good news, worthy of being lifted up mightily on man’s voice. Surely, this is excellent news which being lifted up will cause us to be of good courage. If I am but a brief blip on eternity, and God is eternal, why is it that I live as if the opposite is true? Why do I value the temporary over the eternal? Why do I live as if I will live forever and my creature comforts will last forever? Why do I live in fear of temporal hardship? Why do I fear men instead of God? Why do I live to please men instead of God? How can I go twenty-four hours without remembering to lift up with a mighty voice, “Here is your God!”? God, help me in my unbelief.