Verse 15. - As for man, his days are as grass. Here is a new departure. From the loving kindness and mercy of God the psalmist passes to the weakness and helplessness of man. Man is like grass (Psalm 37:2; Psalm 90:5, 6; Psalm 102:11; Isaiah 40:6-8, etc.). His days fleet and fade. He never "continueth in one stay." As a flower of the field (comp. Job 14:2; Isaiah 28:1; Isaiah 40:6; James 1:10; 1 Peter 1:24, etc.). He flourisheth; i.e. he cometh up in full vigour, glorious to look upon, rejoicing in his youth and strength, but within a little time he fadeth, falleth away, or is "cut down, dried up, and withered." There is no strength or stability in him.

103:15-18 How short is man's life, and uncertain! The flower of the garden is commonly more choice, and will last the longer, for being sheltered by the garden-wall, and the gardener's care; but the flower of the field, to which life is here compared, is not only withering in itself, but exposed to the cold blasts, and liable to be cropt and trod on by the beasts of the field. Such is man. God considers this, and pities him; let him consider it himself. God's mercy is better than life, for it will outlive it. His righteousness, the truth of his promise, shall be unto children's children, who tread in the footsteps of their forefathers' piety. Then shall mercy be preserved to them.As for man, his days are as grass,.... He himself is like the grass which springs out of the earth; continues on it for a time, and then drops into it; the continuance of the grass is very short, it flourishes in the morning, is cut down at evening, and withers; see Psalm 90:5. As a flower of the field, so he flourisheth; which denotes the goodliness of man, and describes him in his best estate, as possessed of health, riches, honour, and all the gifts and endowments of nature; and yet, with all these, is only like a field flower, exposed to every wind, liable to be cropped by every hand, and to be trampled upon by the beasts of the field; and therefore flourishes not long: so very precarious and uncertain is man in his most flourishing circumstances; see Isaiah 40:6.