Ecclesiastes 3:11 - He has also set eternity in the hearts of men

He has made everything beautiful in its time. He has also set eternity in the hearts of men; yet they cannot fathom what God has done from beginning to end.

He hath made every thing beautiful in his time: also he hath set the world in their heart, so that no man can find out the work that God maketh from the beginning to the end.

He has made everything appropriate in its time He has also set eternity in their heart, yet so that man will not find out the work which God has done from the beginning even to the end.

Ecclesiastes 3:11

Commentary

God has made everything beautiful in its time, or, better, that there is an appropriate time for each activity. He is not so much thinking here of the beauty of God's creation as the fact that every action has its own designated time, and that in its time it is eminently fitting.
Also God has put eternity in man's mind. Though living in a world of time, man has intimations of eternity. Instinctively he thinks of "forever," and though he cannot understand the concept, he realizes that beyond this life there is the possibility of a shoreless ocean of time. Yet God's works and ways are inscrutable to man. There is no way in which we can solve the riddle of creation, providence, or the consummation of the universe, apart from revelation. In spite of the enormous advances of human knowledge, we still see through a glass darkly.

MacDonald, W., & Farstad, A. (1997, c1995). Believer's Bible Commentary : Old and New Testaments (Ec 3:11). Nashville: Thomas Nelson.