As is the generation of leaves, so is that of humanity.
The wind scatters the leaves on the ground, but the live timber
Burgeons with leaves again in the season of spring returning.
So one generation of men will grow while another dies.

[Οἵη περ φύλλων γενεὴ τοίη δὲ καὶ ἀνδρῶν.
φύλλα τὰ μέν τ’ ἄνεμος χαμάδις χέει, ἄλλα δέ θ’ ὕλη
τηλεθόωσα φύει, ἔαρος δ’ ἐπιγίγνεται ὥρη·
ὣς ἀνδρῶν γενεὴ ἣ μὲν φύει ἣ δ’ ἀπολήγει.]

Homer (fl. 7th-8th C. BC) Greek author

The Iliad [Ἰλιάς], Book 6, l. 146ff (6.146-149) (c. 750 BC) [tr. Lattimore (1951)]
    (Source)

Like the race of leaves
The race of man is, that deserves no question; nor receives
My being any other breath? The wind in autumn strows
The earth with old leaves, then the spring the woods with new endows;
And so death scatters men on earth, so life puts out again
Man’s leavy issue.
[tr. Chapman (1611), l. 141ff]

Like leaves on trees the race of man is found,
Now green in youth, now withering on the ground:
Another race the following spring supplies,
They fall successive, and successive rise:
So generations in their course decay;
So flourish these, when those are past away.
[tr. Pope (1715-20)]

For, as the leaves, such is the race of man.
The wind shakes down the leaves, the budding grove
Soon teems with others, and in spring they grow.
So pass mankind. One generation meets
Its destined period, and a new succeeds.
[tr. Cowper (1791), l. 175ff]

As is the race of leaves, even such is the race of men. Some leaves the wind sheds upon the ground, but the fructifying wood produces others, and these grow up in the season of spring. Such is the generation of men; one produces, another ceases.
[tr. Buckley (1860)]

The race of man is as the race of leaves:
Of leaves, one generation by the wind
Is scatter'd on the earth; another soon
In spring's luxuriant verdure bursts to light.
So with our race; these flourish, those decay.
[tr. Derby (1864)]

Even as are the generations of leaves such are those likewise of men; the leaves that be the wind scattereth on the earth, and the forest buddeth and putteth forth more again, when the season of spring is at hand; so of the generations of men one putteth forth and another ceaseth.
[tr. Leaf/Lang/Myers (1891)]

Men come and go as leaves year by year upon the trees. Those of autumn the wind sheds upon the ground, but when spring returns the forest buds forth with fresh vines. Even so is it with the generations of mankind, the new spring up as the old are passing away.
[tr. Butler (1898)]

Even as are the generations of leaves, such are those also of men. As for the leaves, the wind scattereth some upon the earth, but the forest, as it bourgeons, putteth forth others when the season of spring is come; even so of men one generation springeth up and another passeth away.
[tr. Murray (1924)]

Very like leaves upon this earth are the generations of men -- old leaves, cast on the ground by wind, young leaves the greening forest bears when spring comes in. So mortals pass; one generation flowers even as another dies away.
[tr. Fitzgerald (1974)]

Like the generations of leaves, the lives of mortal men.
Now the wind scatters the old leaves across the earth,
now the living timber bursts with the new buds
and spring comes round again. And so with men:
as one generation comes to life, another dies away.
[tr. Fagles (1990), ll. 171-75]