Diamonds are beautiful and valuable gemstones, but their beginning is common carbon, black, dirty, and combustible. Through years of intense heat and high pressure, they become pure and strong. This makes them a good metaphor for spiritual strength; God uses intense outside forces to rid us of impurities and to perfect His strength in us. When we experience the fiery furnace of suffering, whether physical or emotional, whether persecution from without or humiliation from within, God's loving purpose is to make us pure and strong.