Proverbs 27:21-23

Complete Jewish Bible

²¹ The crucible [tests] silver, and the furnace [tests] gold,
    but a person [is tested] by [his reaction to] praise.

²² You can crush a fool in a mortar with a pestle,
along with the grain being crushed;
    yet his foolishness will not leave him.

²³ Take care to know the condition of your flocks,
    and pay attention to your herds.