איוב יד:יט פירוש: רש״י

Stones which the water eroded by constantly passing over them.

it washes away i.e., the flood. its aftergrowth of the stone, to be transformed into dust so that something should grow in it. As the aftergrowths of the harvest grow, so will the aftergrowths of this earth be transformed to stone.

but the hope of man is not so, because as soon as he dies, it is lost forever.