Adam Clarke's Commentary on the Bible

Verse 11 (Ecclesiastes 3:11)

Beautiful in his time - God's works are well done; there are order, harmony, and beauty in them all. Even the caterpillar is a finished beauty in all the changes through which it passes, when its structure is properly examined, and the ends kept in view in which each change is to issue. Nothing of this kind can be said of the works of man. The most finished works of art are bungling jobs, when compared with the meanest operation of nature.

He hath set the world in their heart - העולם haolam , that hidden time - the period beyond the present, - Eternity. The proper translation of this clause is the following: "Also that eternity hath he placed in their heart, without which man could not find out the work which God hath made from the commencement to the end." God has deeply rooted the idea of eternity in every human heart; and every considerate man sees, that all the operations of God refer to that endless duration. See Ecclesiastes 3:14 . And it is only in eternity that man will be able to discover what God has designed by the various works he has formed.

- Adam Clarke's Commentary on the Bible