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.

A sound heart is the life of the flesh - A healthy state of the blood, and a proper circulation of that stream of life, is the grand cause, in the hand of God, of health and longevity. If the heart be diseased, life cannot be long continued.

A sound heart is the life of the flesh,.... A heart made so by the grace of God, in which are sound principles of truth, righteousness, and holiness; these preserve from sin, and so from many diseases; whereby the life of the flesh or body is kept safe and sound, or that is kept in health and vigour; or a "quiet heart" (h); a heart free from wrath, anger, and envy, and such like passions and perturbations; this contributes much to the health of the body, and the comfort of life: or a "healing heart", or "spirit" (i); that is humane, kind, and friendly; that pities and heals the distresses of others, and makes up differences between persons at variance: such an one is "the life of fleshes" (k), as in the original text; or of men, of the same flesh and blood; the life of others, as well as of his own flesh; such an one contributes to the comfortable living of others as well as of himself;
but envy the rottenness of the bones; a man that envies the happiness and prosperity of others, this preys upon his own spirits, and not only wastes his flesh, but weakens and consumes the stronger parts of his body, the bones; it is as a "moth" within him, as the Arabic version: the Targum is,
"as rottenness in wood, so is envy in the bones;''
hence Ovid (l) calls it "livor edax", and so Martial (m).
(h) "cor leve", Baynus; "cor lene", Mercerus; "cor lenitatis", Gejerus, so Ben Melech. (i) "Animus sanans", Junius & Tremellius, so the Tigurine version; "sanator", Gussetius, p. 800. (k) "vitae carnium", Montanus; "vita carnium", V. L. Pagninus, Michaelis. (l) Amorum, l. 1. Eleg. 15. v. 1. & de Remed. Amor. l. 1. in fine. (m) Epigr. l. 11. Ep. 21.

An upright, contented, and benevolent mind, tends to health.

A sound heart--both literally and figuratively, a source of health; in the latter sense, opposed to the known effect of evil passions on health.

30 A quiet heart is the life of the body,
But covetousness is rottenness in the bones.
Heart, soul, flesh, is the O.T. trichotomy, Psalm 84:3; Psalm 16:9; the heart is the innermost region of the life, where all the rays of the bodily and the soul-life concentrate, and whence they again unfold themselves. The state of the heart, i.e., of the central, spiritual, soul-inwardness of the man, exerts therefore on all sides a constraining influence on the bodily life, in the relation to the heart the surrounding life. Regarding לב מרפּא, vid., at Proverbs 12:18. Thus is styled the quiet heart, which in its symmetrical harmony is like a calm and clear water-mirror, neither interrupted by the affections, nor broken through or secretly stirred by passion. By the close connection in which the corporeal life of man stands to the moral-religious determination of his intellectual and mediately his soul-life - this threefold life is as that of one personality, essentially one - the body has in such quiet of spirit the best means of preserving the life which furthers the well-being, and co-operates to the calming of all its disquietude; on the contrary, passion, whether it rage or move itself in stillness, is like the disease in the bones (Proverbs 12:4), which works onward till it breaks asunder the framework of the body, and with it the life of the body. The plur. בּשׂרים occurs only here; Bttcher, 695, says that it denotes the whole body; but בּשׂר also does not denote the half, בשׂרים is the surrogate of an abstr.: the body, i.e., the bodily life in the totality of its functions, and in the entire manifoldness of its relations. Ewald translates bodies, but בשׂר signifies not the body, but its material, the animated matter; rather cf. the Arab. âbshâr, "corporeal, human nature," but which (leaving out of view that this plur. belongs to a later period of the language) has the parallelism against it. Regarding קנאה (jealousy, zeal, envy, anger) Schultens is right: affectus inflammans aestuque indignationis fervidus, from קנא, Arab. ḳanâ, to be high red.

A sound heart - Free from envy and inordinate passions. Is life - Procures and maintains the health and vigour of the body.