In the second clause, "destroyeth life" might have been expected as the antithesis to "delivereth souls." But what worse could be said? "A deceitful witness speaketh lies." All destruction is implied in falsehood.

A true witness delivereth souls,.... Or, "a witness of truth" (x): one that witnesses truth upon oath in a court of judicature, he "delivers souls"; men, not one man only, but many; a whole family, or more, in danger of being ruined; he delivers them, as the Septuagint and Arabic versions add, "from evils"; from evil charges and accusations brought against them; from the oppression of their enemies, from the loss of their good name, and from ruin and destruction, that otherwise would have come upon them; he delivers their "lives" (y), as it may be rendered, in danger of being lost by false accusations: so a witness of the truth of Christ, or a faithful minister of the Gospel, not only saves himself, but them that hear him; and is an instrument of delivering the souls of men from error and damnation;
but a deceitful witness speaketh lies; boldly, openly, by wholesale; he blows them out (z), to the ruin of the good names and characters, and to the destruction of the lives, of the innocent; and so a false teacher, one that lies in wait to deceive, speaks lies in hypocrisy, doctrinal lies, to the ruin of the souls of men. The Targum is,
"he that speaketh lies is deceitful;''
he is "deceit" (a) itself, as in the Hebrew text. Such is the man of sin, and such are his emissaries.
(x) "testis veritatis", Montanus, Cocceius, Schultens. (y) "vitas; animam pro vita usurpari notum", Gejerus. (z) "efflat", Tigurine version, Piscator, Gejerus; "spirat", Schultens; "efflabit", Monatnus. (a) "dolus", Montanus, Vatablus; "fraus", Cocceius.

An upright man will venture the displeasure of the greatest, to bring truth to light.

Life often depends on truth-telling.
a deceitful . . . lies--He that breathes out lies is deceit, not to be trusted (Proverbs 14:5).

25 A witness of truth delivereth souls;
But he who breathes out lies is nothing but deception.
When men, in consequence of false suspicions or of false accusations, fall into danger of their lives (דיני נפשׁות is the designation in the later language of the law of a criminal process), then a tongue which, pressed by conscientiousness and not deterred by cowardice, will utter the truth, saves them. But a false tongue, which as such (vid., Proverbs 14:5) is a יפח כזבים (after the Masora at this place ויפח, defective), i.e., is one who breathes out lies (vid., regarding יפיח at Proverbs 6:19), is mere deception (lxx, without reading מרמּה [as Hitzig does]: δόλιος). In Proverbs 12:17 מרמה is to be interpreted as the object. accus. of יגיד carried forward, but here to carry forward מצּיל (Arama, Lwenstein) is impracticable - for to deliver deceit = the deceiver is not expressed in the Hebr. - מרמה is, as possibly also Hebrews 12:16 (lxx δόλιος), without אישׁ or עד being supplied, the pred. of the substantival clause: such an one is deception (in bad Latin, dolositas), for he who utters forth lies against better knowledge must have a malevolent, deceitful purpose.

Souls - Such as are innocent, from false accusations.