What does it mean that a merry heart does good (Proverbs 17:22)?

On the other hand, a joyful (not a vain or thoughtless) heart is an excellent medicine in this world of aches and bruises; as surely as a spirit shattered by affliction and charged with grief and fear dries up the bones, making one a skeleton rather than a human being (v. 22). Man lives not by bread alone, still less bitter herbs, but by God's Word that reveals His grace in Christ.

"A merry heart does good like a medicine" (v. 22). Of course, the only who is entitled to have a merry heart is a believer, though some are more happy than others. If so, they do good in encouraging others. A broken spirit will have the opposite effect, and if this malady affects a believer, he should immediately seek the grace of God to overcome it.

On the banks of the future river that will flow from the sanctuary, trees will grow, of which it is said, "The fruit thereof shall be for meat, and the leaf thereof for medicine." Ezek. 47:12. This agrees with Rev. 22:2. The prophet Jeremiah twice observes that when God brings His judgements upon a people, no medicine will cure them. Jer. 30:13; Jer. 46:11. Prov. 17:22 says, "A merry heart doeth good like a medicine," or 'promoteth healing.'

But how true all this is to the sensibilities of our common humanity! We all understand it. The Lord's heart was merry, as I may say, in John 4; but there was nothing to make it merry in Mark 4. And we are taught to know (and our experience sets to its seal that the word is true) "that a merry heart doeth good like medicine, but a broken spirit drieth the bones." (Prov. 17:22.) So that the Master can say in the one case, "I have meat to eat that ye know not of," while in the other, He will use the pillow which care for His weariness had provided.

Hygienics: As we think of the numberless rules about the laws of health, with all sorts of prescriptions of exercise and diet, we can understand how a sober knowledge of the word of God, with its primary principle that "a merry heart doeth good like a medicine," would cast a flood of light upon a valuable and important part of medical practice. How wide-reaching, and simple too, is the direction that we present our "bodies a living sacrifice, holy, and acceptable unto God," our "reasonable service"; which, while it does not provide for bodily exercise which profiteth for a little, does secure that treatment of the body which will ensure its most efficient and harmonious activity. Godliness hath "promise of the life which now is and that which is to come."

No; only an inward medicine can produce the shining face. It is from inside that its light comes. The wise man knew something of this when he wrote, “A merry heart does good like a medicine” (Prov. 17:22).

And wherein lies the secret of a merry heart? It is not found in the worldling. His gaiety is forced, “as the crackling of thorns under a pot, so is the laughter of the fool” (Ecc. 6:6). His merriment is not spontaneous. It is dependent on his circumstances.

A heart full of Joy is a life full of power.

This joy lifts the heart above all circumstances so that we can "rejoice in the Lord always" "and, like the psalmist, can prove the truth of the words, "Delight thyself also in the Lord, and he shall give thee the desires of thine heart." Thus "the joy of the Lord is our strength," and though in our service we may go forth weeping, yet, if bearing precious seed, we shall doubtless come again with joy bringing our sheaves with us; for they that sow in tears shall reap in joy.

"Restore unto me the joy of Thy salvation; and let a willing spirit sustain me." For heaviness of heart enfeebles both walk and work: the joy of the Lord gives strength and courage. We may not make light of emotion. Our care is to be that it be justified with knowledge and connected with practical result. "The fruit of the Spirit is love; joy, peace" (Gal. 5:22); but then "long-suffering; gentleness; goodness, meekness; temperance;" follow after these and sustain them.

Gospel this is, and he realizes it as such: "make me to hear joy and gladness that the bones which Thou hast broken may rejoice." It is only prayer as yet however; but a divinely taught prayer surely. We too; if the gospel be "good news;" ought to have the joy of the gospel; and healthful; medicinal it is; even for crushed bones. "The joy of the Lord is your strength."