7 Rivers run into the sea, but the sea is never full. Then the water returns again to the rivers and flows out again to the sea.

Matthew Henry's Commentary on Ecclesiastes 1:7

Commentary on Ecclesiastes 1:4-8

(Read Ecclesiastes 1:4-8)

All things change, and never rest. Man, after all his labour, is no nearer finding rest than the sun, the wind, or the current of the river. His soul will find no rest, if he has it not from God. The senses are soon tired, yet still craving what is untried.