Charles Ellicott Commentary Isaiah 40:7

"The grass withereth, the flower fadeth, because the breath of Jehovah bloweth upon it; surely the people is grass." — Isaiah 40:7 (ASV)

The spirit of the Lord blows upon it. —This is better understood as the breath, or the wind of Jehovah, as we are still in the realm of the parable, and the agency is destructive, not life-giving.

A “wind of Jehovah” would be a mighty storm-blast, tearing up the grass and hurling it to destruction.

The image of the fading flower reminds us of the well-known Homeric simile, “As are the generations of leaves, so are those of men” .

The word of our God ... —This primarily refers to the prophetic word revealing the will of God, but it also includes all manifestations of His being (Psalms 119:41; Psalms 119:65; Psalms 119:89; John 1:1).