"Iron sharpens iron" is found in Proverbs 27.17: "Just as iron sharpens iron, so a man is sharpened by contact with his neighbor." By rubbing two iron blades together, both will become sharper and be able to cut more effectively. In the same way, God's Word is a "two-edged sword" (Hebrews 4.12) with which we must sharpen each other through our meetings, fellowship and other interactions...