'Working' in the Bible

Then I saw all the works which my hands had made, and everything I had been working to do; and I saw that all was to no purpose and desire for wind, and there was no profit under the sun.

It is one who is by himself, without a second, and without son or brother; but there is no end to all his work, and he has never enough of wealth. For whom, then, am I working and keeping myself from pleasure? This again is to no purpose, and a bitter work.

The sleep of a working man is sweet, if he has little food or much; but to him who is full, sleep will not come.

And this again is a great evil, that in all points as he came so will he go; and what profit has he in working for the wind?