In the morning it flourisheth - This does not mean that it grows with any special vigor or rapidity in the morning, as if that were illustrative of the rapid growth of the young; but merely that, in fact, in the morning it is green and vigorous, and is cut down in the short course of a day, or before evening. The reference here is to grass as an emblem of man.
And groweth up - The same word in the Hebrew which is used in the close of the previous verse.
In the evening it is cut down, and withereth - In the short period of a day. What was so green and flourishing in the morning, is, at the close of the day, dried up. Life has been arrested, and death, with its consequences, has ensued. So with man. How often is this literally true, that those who are strong, healthy, vigorous, hopeful, in the morning, are at night pale, cold, and speechless in death! How striking is this as an emblem of man in general: so soon cut down; so soon numbered with the dead. Compare the notes at Isaiah 40:6-8; notes at 1-Peter 1:24-25.

In the morning it flourisheth and groweth up,.... That is, the grass, through the dew that lay all night on it, and by the clear shining of the sun after rain, when it appears in great beauty and verdure; so man in the morning of his youth looks gay and beautiful, grows in the stature and strength of his body, and in the endowments of his mind; and it may be also in riches and wealth; it is well if he grows in grace, and in the knowledge of Christ:
in the evening it is cut down, and withereth; the Targum adds, "through heat"; but it cannot be by the heat of the sun, when it is cut down at evening; but it withers in course, being cut down. This respects the latter part of life, the evening of old age; and the whole expresses the shortness of life, which is compared to grass, that now is in all its beauty and glory, and tomorrow is cast into the oven, Matthew 6:30. This metaphor of grass, to set forth the frailty of man, and his short continuance, is frequently used; see Psalm 37:2, 1-Peter 1:24. It may be observed, that man's life is represented but as one day, consisting of a morning and an evening, which signifies the bloom and decline of life.