Mark Driscoll Discusses the Power of the Tongue

Proverbs 17:22
A joyful heart is good medicine,
but a crushed spirit dries up the bones. (ESV)
A cheerful disposition is good for your health;
gloom and doom leave you bone-tired. (Message)
Some Good Commentary:
22 One's psychological condition affects one's physical condition: a healthy attitude fosters good health but a depressed spirit ruins health. The antithetical idea, describing the two effects, stresses the importance of a cheerful heart. The first line presents the ideal: a "cheerful heart" (leh game-h) causes "good healing" (yetih gehah; NIV, "is good medicine"). The heart, as with the spirit in v.22b, refers to the mind, the psyche. The positive and healthy outlook on life brings healing. On the other hand, a "crushed spirit" (rush neke'ah), i.e., one that is depressed or dejected, has an adverse effect on the health of the body. "Bones" figuratively represents the body (encased in the bony frame): fat bones means a healthy body (3:8; 15:30; 16:24), but dry bones signify unhealthiness and lifelessness (cf. Ezek 37:1-14).

Proverbs 18:21
Death and life are in the power of the tongue,
and those who love it will eat its fruits. (ESV)

Words kill, words give life;
they’re either poison or fruit—you choose. (Message)
Some Good Commentary:
21 Many a one has been his own death by a foul tongue, or the death of others by a false tongue. and, on the contrary, many a one has saved his life' by a prudent gentle tongue, and saved the lives of others by intercession (an interposing or pleading on behalf of another person; a prayer to God on behalf of another) for them.