All the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come, thither they return again.
All the rivers run into the sea ... unto the place from whence the rivers come there they return - as is proved by the fast that --
The sea is not full. They return to their sources through the medium of the clouds (Genesis 2:6). By subterraneous cavities, and by evaporation forming rain clouds, the fountains and rivers are supplied from the sea, into which they then flow back. The sun lifts out of the sea as much water as flows into it, which the winds carry as vapour to the dry land, where the hills, with their cold summits, condense it into rain, which having watered the earth, the surplus finds its way to the rivers, and thence into the sea again. The connection is: just as the sun, wind, and rivers are ever shifting about, while the cycle in which they move is invariable, they return to the point whence they set out; so man moves in the same circle, never moving forward beyond vanity; his old misery ever recurs (cf. "there is no new thing," Ecclesiastes 1:9).