Ecclesiastes 8:7; Ecclesiastes 8:15; Ecclesiastes 8:17

7 For he doesn't know that which will be; for who can tell him how it will be?
15 Then I commended mirth, because a man has no better thing under the sun, than to eat, and to drink, and to be joyful: for that will accompany him in his labor all the days of his life which God has given him under the sun.
17 then I saw all the work of God, that man can't find out the work that is done under the sun, because however much a man labors to seek it out, yet he won't find it. Yes, moreover, though a wise man thinks he can comprehend it, yet he won't be able to find it.