Proverbs 27:17-22

As iron sharpens iron, So one man sharpens [and influences] another [through discussion]. He who tends the fig tree will eat its fruit, And he who faithfully protects and cares for his master will be honored. [1 Cor 9:7, 13] As in water face reflects face, So the heart of man reflects man. Sheol (the place of the dead) and Abaddon (the underworld) are never satisfied; Nor are the eyes of man ever satisfied. [Prov 30:16; Hab 2:5] The refining pot is for silver and the furnace for gold [to separate the impurities of the metal], And each is tested by the praise given to him [and his response to it, whether humble or proud]. Even though you pound a [hardened, arrogant] fool [who rejects wisdom] in a mortar with a pestle like grain, Yet his foolishness will not leave him.