'Toiling' in the Bible

A man who is all alone with no companion, he has no children nor siblings; yet there is no end to all his toil, and he is never satisfied with riches. He laments, "For whom am I toiling and depriving myself of pleasure?" This also is futile and a burdensome task!

This is another misfortune: Just as he came, so will he go. What did he gain from toiling for the wind?