John Gill - Exposition
John Gill
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...