Isaiah 40:7

יָבֵשׁ חָצִיר נָבֵל צִיץ כִּי רוּחַ יְהוָה נָשְׁבָה בּוֹ אָכֵן חָצִיר הָעָם

7 The grass withers, flowers fade, because the breath of the LORD blows on it. Surely the people are grass.

יָבֵשׁ חָצִיר  The grass withers, יָבֵשׁ is a stative verb, qal perfect 3 m sg from the root יבש, "to be dry, wither."

נָבֵל צִיץ  flowers fade, נָבֵל is also said to be a stative verb: qal pf 3 sg from נבל. The vowel pattern of both these verbs deviates from the qal, looking much more like the peal (pa-el) forms found in Aramaic (e.g. קָטֵל). In the Bible, flowers are most often a symbol of death, especially in the Old Testament. This isn't a happy message.

כִּי רוּחַ יְהוָה נָשְׁבָה בּוֹ  because the breath of the LORD blows on it. qal feminine 3rd sg from שָׁבָה, "to blow." This verb is most often found in the piel.

אָכֵן חָצִיר הָעָם  Surely the people are grass. אָכֵן is not a common word. It's an adverb that occurs less than twenty times, but four of them are in Isaiah (40:7; 45:15; 49:4; 53:4).

The prophet reflects the words of Job ("He springs up like a flower and withers away," Job 14:2). The image of flowers in the Bible is rarely a pretty one. Apart from decorations carved into the furnishings of the tabernacle and temple (Exodus 25:33-34; 37:19-20, 2 Chron. 4:5, etc.), a dozen or so references in the Song of Songs (2:1-2; 4:5; 5:13; 6:2-3; 7:2, etc.), some song titles (titles of Psalms 45, 69 and 80) and Jesus' references to the lilies (Matthew 6:28), almost all the references to flowers in the Bible are about decay or judgment:

"(Man's day) flourishes like a flower of the field; the wind blows over it and it is gone," (Psalm 103:15-16).

"When the blossom is gone and the flower becomes a ripening grape, he will cut off the shoots with pruning knives," (Isaiah 18:5).

"He will pass away like a wild flower" (James 1:10).

The exception is the gospel promise God made through Hosea when Isaiah was a young man: "I will heal their waywardness and love them freely, for my anger has turned away from them. I will be like the dew to Israel; he will blossom like a lily" (Hosea 14:4-5).