Ecclesiastes 4:4, 8

I have seen that every labor and every skill which is done is the result of rivalry between a man and his neighbor. This too is vanity and striving after wind.

There was a certain man without a dependent, having neither a son nor a brother, yet there was no end to all his labor. Indeed, his eyes were not satisfied with riches and he never asked, “And for whom am I laboring and depriving myself of pleasure?” This too is vanity and it is a grievous task.