Ecclesiastes 2:20 in the King James Version
Therefore I went about to cause my heart to despair of all the labour which I took under the sun.
Context
19 Who knows whether he will be a wise man or a fool? Yet he will have rule over all of my labor in which I have labored, and in which I have shown myself wise under the sun. This also is vanity.
20 Therefore I began to cause my heart to despair concerning all the labor in which I had labored under the sun.
21 For there is a man whose labor is with wisdom, with knowledge, and with skillfulness; yet he shall leave it for his portion to a man who has not labored for it. This also is vanity and a great evil.