A sound heart is the life of the flesh: but envy the rottenness of the bones.
– Proverbs 14:30
The word for sound means healthy or whole, and heart refers figuratively to the mind. We must guard our minds and feed them with sound wisdom to guard our life (Proverbs 4:23; Philippians 4:8). Wisdom affects our overall health as does folly (Proverbs 17:22). The contrast here is with envy, or jealousy. Envy, bitterness, resentment, anger, and all such thoughts and feelings are those that eat away at a man mentally, emotionally, and physically.