Through knowledge - Better, By the knowledge of the just, shall they (i. e., the neighbors) be delivered.

A hypocrite with his mouth - חנף chaneph might be better translated infidel than hypocrite. The latter is one that pretends to religion; that uses it for secular purposes. The former is one who disbelieves Divine revelation, and accordingly is polluted, and lives in pollution. This is properly the force of the original word. Such persons deal in calumny and lies, and often thus destroy the character of their neighbor. Besides, they are very zealous in propagating their own infidel notions; and thus, by this means, destroy their neighbor; but the experimental knowledge which the just have of God and his salvation prevents them from being ensnared.

An (d) hypocrite with [his] mouth destroyeth his neighbour: but through knowledge shall the just be delivered.
(d) A deceiver who pretends friendship, but privately is an enemy.

An hypocrite with his mouth destroyeth his neighbour,.... Deceives him with his flatteries and lies, and draws him into destructive schemes and practices; or "corrupts" him, as the word (i) signifies, and as the Targum renders it, with false doctrines; so, with fair words and good speeches, such who lie in wait to deceive impose upon the simple and credulous; and false teachers, with their damnable heresies, bring swift destruction on men; and particularly antichrist and his emissaries, through speaking lies in hypocrisy, corrupt and destroy many, 1-Timothy 4:1;
but through knowledge shall the just be delivered; from the hypocrite and deceitful worker, and from being corrupted and destroyed by the words of his mouth: Jarchi says, through the knowledge of the law, which warns against him; but rather through the knowledge of the Gospel, which the just man has; for as by this such escape the pollutions of the world, so likewise they are delivered, are kept and secured, from the error of the wicked: through a man's knowledge of himself, of his descent from Adam, of the corruption of his nature, of the plague of his heart, and the exceeding sinfulness of sin; of his lost and undone state; of his impotency to that which is good, of his incapacity to fulfil the law, and atone for sin; and of the insufficiency of his own righteousness to justify him before God; he is delivered and preserved from giving into the notions of the purity of human nature, the power of free will, and the doctrine of justification by works: through his knowledge of the person of Christ; of his offices and relations; of him as a Saviour; of the efficacy of his blood, the excellency of his righteousness, and the completeness of his sacrifice; and through the knowledge of God in Christ, and of the Spirit and of his operations of grace, as well as of the sacred Scriptures in general; he is safe from being carried away with any errors concerning any of the divine Persons, particularly concerning the deity, sonship, and satisfaction of Christ; in short, as ignorance is the mother of devotion, superstition, and error, in the church of Rome, spiritual experimental knowledge of the above things is the best preservative from all errors and heresies which corrupt and destroy the souls of men, to be found in that apostate church, or elsewhere.
(i) "corrumpet", Schultens; so Pagninus, Montanus; "corrumpit", Vatablus, Junius & Tremellius, Piscator, Mercerus, Gejerus.

Hypocrites delude men into error and sin by artful objections against the truths of God's word.

(Compare Psalm 35:16; Daniel 11:32). The just is saved by superior discernment.

9 The wicked with his mouth prepareth destruction for his neighbour;
But by knowledge the righteous are delivered from it.
The lxx translate, ἐν στόματι ἀσεβῶν παγὶς (רשׁת?) πολίταις, αἴσθησις δὲ δικαίοις εὔοδος, (יצלחו). There is no reason for changing (with Hitzig and Ewald) the text, which in the form in which it is here translated was before all other translators (Aq., Symmachus, Theodotion, Syr., Targ., Jerome). The accentuation, which separates the two instrumental statements by greater disjunctives from that which follows, is correct. The "three" Greek versions viz. of Aquila, Theodotion, and Symmachus translate חנף by ὑποκριτής, which it means in the modern idiom; but in the ancient Hebr. it signifies, him who is resolved upon evil, as in Arab. ḥanyf, him who is resolved upon that which is right: he who turns aside to evil enters on a path far removed from that which is right. In ישׁחית one is reminded (without any etymological reason) of שׁחת (pit), and so in יחלצוּ of משּׁחיתותם (Psalm 107:20) or a similar word; but בּדּעת contains the reference, in this connection not easy to be mistaken, to the hostile purposes of the wicked masked by the words of the mouth, which are seen through by the righteous by virtue of knowledge which makes them acquainted with men. This penetrating look is their means of deliverance.

Delivered - From the infection of the hypocrite's evil counsel.