Proverbs 27:17-22

As iron sharpens iron, so a friend sharpens a friend. As workers who tend a fig tree are allowed to eat the fruit, so workers who protect their employer’s interests will be rewarded. As a face is reflected in water, so the heart reflects the real person. Just as Death and Destruction are never satisfied, so human desire is never satisfied. Fire tests the purity of silver and gold, but a person is tested by being praised. You cannot separate fools from their foolishness, even though you grind them like grain with mortar and pestle.