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

7 No one is certain what is to be, and who is able to say to him when it will be?

15 So I gave praise to joy, because there is nothing better for a man to do under the sun than to take meat and drink and be happy; for that will be with him in his work all the days of his life which God gives him under the sun.

17 Then I saw all the work of God, and that man may not get knowledge of the work which is done under the sun; because, if a man gives hard work to the search he will not get knowledge, and even if the wise man seems to be coming to the end of his search, still he will be without knowledge.