William Burkitt on 1 Peter 1:24

Our apostle closes the chapter, by setting before them the excellency of their spiritual regenerate state, compared with all other excellences and endowments whatsoever: All flesh, that is, flesh with all its glory, is a fading, dying, perishing thing; it flags like the grass, and fades like the flower: sweetness, which affects the smell; beauty, that affects the eye; softness and smoothness, which affect the touch; all these our apostle passes over, and speaks of the flower, not as flourishing, but as withering; not as springing up, but as falling away. The grass withereth the flower falleth away.

Learn hence, That man, when most flourishing, with all the ornaments of wit and wealth, beauty and honour, is fading, and near to withering.--Thus David describes them, As for man, his days are as grass; as the flower of the field so he flourishes; the wind passeth over it and it is gone. Ps 103:15-16 Though the flower be neither cut nor cropt, yet a breath of wind blasts it, and blows away the beauty of it: All flesh is as grass, and all the glory of man as the flower of grass.