Proverbs 27:22 in the World English Bible
Though you grind a fool in a mortar with a pestle along with grain, yet his foolishness will not be removed from him.
Context
21 As the fining pot for silver, and the furnace for gold; so is a man to his praise.
22 Though thou shouldest bray a fool in a mortar among wheat with a pestle, yet will not his foolishness depart from him.
23 Be thou diligent to know the state of thy flocks, and look well to thy herds.