Ecclesiastes 2:20-23

So I turned aside and let my heart despair over all the fruit of my labor for which I had labored under the sun. For there is a man who has labored with wisdom and knowledge and skill, yet gives his legacy to one who has not labored for it. This too is vanity and a great evil. For what does a man get from all his labor and from the striving and sorrow of his heart with which he labors under the sun? For all his days his work is painful and sorrowful; even at night his mind does not rest. This too is vanity (worthless).