Albert Barnes Commentary Proverbs 14:30

"A tranquil heart is the life of the flesh; But envy is the rottenness of the bones." — Proverbs 14:30 (ASV)

Sound heart - literally, “heart of health,” that in which all emotions and appetites are in a healthy equilibrium. The contrast with this is the envy which eats, like a consuming disease, into the very bones and marrow of a man’s moral life.