Ecclesiastes 1:13; Ecclesiastes 2:23; Ecclesiastes 2:26; Ecclesiastes 3:10; Ecclesiastes 5:3; Ecclesiastes 5:14; Ecclesiastes 8:16

13 And I set my heart to seek and search out by wisdom concerning all that is done under heaven; this burdensome task God has given to the sons of man, by which they may be exercised.
23 For all his days are sorrowful, and his work burdensome; even in the night his heart takes no rest. This also is vanity.
26 For God gives wisdom and knowledge and joy to a man who is good in His sight; but to the sinner He gives the work of gathering and collecting, that he may give to him who is good before God. This also is vanity and grasping for the wind.
10 I have seen the God-given task with which the sons of men are to be occupied.
3 For a dream comes through much activity, And a fool's voice is known by his many words.
14 But those riches perish through misfortune; When he begets a son, there is nothing in his hand.
16 When I applied my heart to know wisdom and to see the business that is done on earth, even though one sees no sleep day or night,