Proverbs 27:17-21

Iron sharpens iron, and one man sharpens another. Whoever tends a fig tree will eat its fruit, and he who guards his master will be honored. As in water face reflects face, so the heart of man reflects the man. Sheol and Abaddon are never satisfied, and never satisfied are the eyes of man. The crucible is for silver, and the furnace is for gold, and a man is tested by his praise.