Heaviness in the heart of a man maketh it stoop - Sorrow of heart, hopeless love, or a sense of God's displeasure - these prostrate the man, and he becomes a child before them.
But a good word maketh it glad - A single good or favorable word will remove despondency; and that word, "Son, be of good cheer, thy sins are forgiven thee," will instantly remove despair.

Heaviness in the heart of man weigheth it down: but a (k) good word maketh it glad.
(k) That is, words of comfort, or a cheerful mind which is declared by his words, rejoices a man, as a covetous mind kills him.

Heaviness in the heart of man maketh it stoop,.... Either an anxious care and solicitude about living in the world, as the word (m) signifies; when it seizes a man's spirits, it depresses them, and keeps them down: or a fear and dread of adversity, or sorrow and grief, on account of some calamity and distress; when it gets into a man's heart, it sinks and bows it down, that it cannot take any pleasure or comfort in anything. The Septuagint and Arabic versions render it, a "terrible word troubles the heart of a just man"; or "troubles the heart of man", as the Syriac version; the Targum is,
"a word of fear in the heart of man causes fear:''
such is the law, which is a word of terror; which speaks terrible things to men; fills the mind with terror; works wrath in the conscience, and induces a spirit of bondage to fear; bows and keeps under the spirits of men, through a fearful looking for of judgment and fiery indignation;
but a good word maketh it glad; a comforting, cheering, and encouraging word from any friend, that compassionates their distressed case; this lifts up the heart and inspires it with joy; so a word in season, spoken by a Gospel minister, raises up a soul that is bowed down, and gives it comfort and joy: such a good word is the Gospel itself; it is good news from a far country, which is like cold water to a thirsty soul, very refreshing and reviving. The Septuagint and Arabic versions here render it, "a good message", and such the Gospel is; which, when brought to the heart of a poor sinner, depressed with the terrors of the law, causes joy in it; such is the word of peace, pardon, righteousness, and eternal life by Christ; such is the word that he himself spoke, Matthew 9:2. Kimchi instances in Psalm 55:22.
(m) "solicitudo", Tigurine version, Montanus, Piscator, Michaelis; "solicitudo anxia", Mercerus, Gejerus; "solicita anxietas", Junius & Tremellius; "anxietatem", Schultens.

Care, fear, and sorrow, upon the spirits, deprive men of vigour in what is to be done, or courage in what is to be borne. A good word from God, applied by faith, makes the heart glad.

a good word--one of comfort.

25 Trouble in the heart of a man boweth it down,
And a friendly word maketh it glad.
The twofold anomaly that דּאגה is construed as masc. and לב as fem. renders the text doubtful, but the lxx, Syr., Targum, which introduce another subject, φοβερὸς λόγος (דּבר מדאיג?), do not improve it; Theodotion's is preferable, who translates μέριμνα ἐν καρδίᾳ ἀνδρὸς κατίσχει αὐτόν, and thus reads ישׁחנּוּ. But the rhyme is thereby lost. As כּבוד, Genesis 49:6, so also may לב be used as fem., for one thereby thinks on נפשׁ; the plur. לבּות (לבבות), according to which in Ezekiel 16:30 we find the sing. לבּה, may also conform to this. And ישׁחנה as pred. to דאגה follows the scheme Proverbs 2:10, perhaps not without attractional co-operation after the scheme קשׁת גברים חתים, 1-Samuel 2:4. השׁחה, from שׁחה, occurs only here; but השׁח, from שׁחח, occurs only twice. דּבר טוב designates in the book of Joshua and in Kings (1-Kings 8:56) the divine promise; here it is of the same meaning as 1-Kings 12:7 : an appeasing word. Who has not in himself had this experience, how such a word of friendly encouragement from a sympathizing heart cheers the sorrowful soul, and, if only for a time, changes its sorrow into the joy of confidence and of hope!

A good word - A compassionate or encouraging word.