A wholesome tongue - literally, as in the margin, the same word as "sound" in Proverbs 14:30 (see the note). A more literal rendering would be soundness of speech.
Tree of life - Compare Proverbs 3:18 note.
Breach in the spirit - With the sense of vexation (compare Isaiah 65:14).

A wholesome tongue is a tree of life - Here again is an allusion to the paradisiacal tree, עץ חיים ets chaiyim, "the tree of lives."

A wholesome tongue is a tree of life,.... A tongue that delivers out salutary instructions, wholesome advice and counsel; a "healing tongue" (w), as it may be rendered, which pacifies contending parties, and heals the divisions between them; to have the benefit of such a man's company and conversation is like being in paradise. Such is the tongue of a Gospel minister, which delivers out the wholesome words of our Lord Jesus Christ; sound speech and doctrines, which cannot be condemned; healing truths to wounded consciences, such as peace, pardon, righteousness, and atonement by the blood of Christ. These are the means of quickening dead sinners, reviving and comforting distressed ones, and show the way of eternal life unto them;
but perverseness therein is a breach in the spirit; impure, unchaste, unsavoury, and corrupt language, does mischief to the spirits of men; evil communications corrupt the heart and manners, defile the soul and the conversation; these and unsound doctrines eat as a canker; and as they make the heart of God's people sad, whom he would not have made sad; so they bring distress and despair into the spirits of others, and make sad wounds and breaches there, which are never healed, and that both in the spirits of speakers and hearers; for damnable heresies bring swift destruction on the propagators of them, and them that receive them.
(w) "sanans", so some in Vatablus.

A good tongue is healing to wounded consciences, by comforting them; to sin-sick souls, by convincing them; and it reconciles parties at variance.

A wholesome tongue--(Compare Margin), pacifying and soothing language.
tree of life-- (Proverbs 3:18; Proverbs 11:30).
perverseness therein--cross, ill-natured language.
breach . . . spirit--(compare Isaiah 65:14, Hebrew), grieves, instead of appeasing.

4 Gentleness of the tongue is a tree of life;
But falseness in it is a wounding to the spirit.
Regarding מרפּא, vid., at Proverbs 12:18, and regarding סלף, at Proverbs 11:3; this latter word we derive with Fleischer from סלף, to subvert, overthrow, but not in the sense of "violence, asperitas, in as far as violent speech is like a stormy sea," but of perversity, perversitas (Venet. λοξότης), as the contrast to truthfulness, rectitude, kindness. Gentleness characterizes the tongue when all that it says to a neighbour, whether it be instruction or correction, or warning or consolation, it says in a manner without rudeness, violence, or obtrusiveness, by which it finds the easiest and surest acceptance, because he feels the goodwill, the hearty sympathy, the humility of him who is conscious of his own imperfection. Such gentleness is a tree of life, whose fruits preserve life, heal the sick, and raise up the bowed down. Accordingly, שׁבר בּרוּח is to be understood of the effect which goes forth from perversity or falseness of the tongue upon others. Fleischer translates: asperitas autem in ea animum vulnerat, and remarks, "שׁבר ברוח, abstr. pro concreto. The verb שׁבר, and the n. verbale שׁבר derived from it, may, in order to render the meaning tropical, govern the prep. בּ, as the Arab. kaser baḳlby, he has broken my heart (opp. Arab. jabar baḳlaby), cf. בּפניו, Proverbs 21:29, vid., De Glossis Habichtianis, p. 18; yet it also occurs with the accus., Psalm 69:21, and the corresponding gen. שׁבר רוּח, Isaiah 65:14." In any case, the breaking (deep wounding) is not meant in regard to his own spirit, but to that of the neighbour. Rightly Luther: but a lying (tongue) makes heart-sorrow (elsewhere, a false one troubles the cheerful); Euchel: a false tongue is soul-wounding; and the translation of the year 1844: falsehood is a breach into the heart. Only for curiosity's sake are two other interpretations of 4a and 4b mentioned: the means of safety to the tongue is the tree of life, i.e., The Tor (Erachin 15b); and: perversity suffers destruction by a breath of wind, after the proverb, כל שׁישׁ בו גסות רוח רוח קימעא שׁוברתו, a breath of wind breaks a man who is puffed up
(Note: Vid., Duke's Rabbinische Blumenlese, p. 176, where the rendering is somewhat different.)
(which Meri presents for choice, vid., also Rashi, who understands רוח of the storm of judgment). The lxx translates, in 4b, a different text: ὁ δὲ συντηρῶν αὐτὴν πλησθήσεται πνεύματος; but the ישׂבּע רוּח here supposed cannot mean "to be full of spirit," but rather "to eat full of wind." Otherwise the Syr. and Targ.: and he who eateth of his own fruit is satisfied (Hebrews. ואכל מפּריו ישׂבּע) - an attempt to give to the phrase ישׂבע a thought correct in point of language, but one against which we do not give up the Masoretic text.

Wholesome - Which utters sound and useful counsels. Tree of life - Is greatly useful to preserve the present life, and to promote the spiritual and eternal life, both of the speaker and hearers. Perverseness - False or corrupt speeches. A breach - Disturbs and wounds the spirits, both of the speaker and hearers.