Proverbs 27:17-21

It takes a grinding wheel to sharpen a blade, and so one person sharpens the character of another. Tend an orchard and you’ll have fruit to eat. Serve the Master’s interests and you’ll receive honor that’s sweet. Just as no two faces are exactly alike, so every heart is different. Death and destruction are never filled, and the desires of men’s hearts are insatiable. Fire is the way to test the purity of silver and gold, but the character of a man is tested by giving him a measure of fame.