Matthew Henry Commentary Psalms 103:15-18

"As for man, his days are as grass; As a flower of the field, so he flourisheth. For the wind passeth over it, and it is gone; And the place thereof shall know it no more. But the lovingkindness of Jehovah is from everlasting to everlasting upon them that fear him, And his righteousness unto children`s children; To such as keep his covenant, And to those that remember his precepts to do them." — Psalms 103:15-18 (ASV)

How short is man's life, and how uncertain! The flower of the garden is commonly finer and will last longer, because it is 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 is also exposed to the cold blasts, and liable to be cropped and trampled by the animals 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, will extend to children's children who walk in the footsteps of their forefathers' piety. Then mercy will be preserved for them.