Gregory the Dialogist

He cometh forth like a flower, and is crushed: he fleeth also as a shadow, and never continueth in the same state. For, 'as a flower, he cometh forth,' in that he shews fair in the flesh; but he is 'crushed,' in that he is reduced to corruption. For what are men, as born in the world, but a kind of flowers in a field? Let us stretch our interior eyes over the breadth of the present world, and, lo, it is filled as it were with as many flowers as there are human beings. So life in this flesh is the flower in grass. …

Morals on the Book of Job, Book XI ↗

Thomas Aquinas

Second he excludes those things in which a man can take glory; the first among these is the beauty of the body with which a man is strong in his youth. But this glory is nothing because it passes quickly like the flower. So he says, "Who like a flower comes forth and is crushed," easily. The second is fame, which does not last for a long time, and so he says, "and he flees like a shadow." For no trace or memory of a shadow which passes remains. …

Commentary on Job ↗