Though you grind fools in a mortar, grinding them like grain with a pestle, you will not remove their folly from them. (NIV)
Even though like grain you should pound a fool in a mortar with a pestle, yet will not his foolishness depart from him. (AMP)
Though thou shouldest bray a fool in a mortar among wheat with a pestle, yet will not his foolishness depart from him. (KJV)