Ecclesiastes 2:19 in the King James Version
And who knoweth whether he shall be a wise man or a fool? yet shall he have rule over all my labour wherein I have laboured, and wherein I have shewed myself wise under the sun. This is also vanity.
Context
18 I hated all my labor in which I labored under the sun, because I must leave it to the man who comes after me.
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.