'Labors' in the Bible

What does a man gain for all his effortsthat he labors at under the sun?

For what does a man get with all his work and all his efforts that he labors at under the sun?

What profit has he who works in that in which he labors?

This is also a painful tragedy: However a person comes, he also departs; so what does he gain as he labors after the wind?

Behold, here is what I have seen to be good and fitting: to eat and drink, and to find enjoyment in all the labor in which he labors under the sun during the few days of his life which God gives him—for this is his [allotted] reward.

I observed all the work of God and concluded that man is unable to discover the work that is done under the sun. Even though a man labors hard to explore it, he cannot find it; even if the wise man claims to know it, he is unable to discover it.