John Gill's Exposition of the Whole Bible
Proverbs 11:9
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 ישחת "corrumpet", Schultens; so Pagninus, Montanus; "corrumpit", Vatablus, Junius Tremellius, Piscator, Mercerus, Gejerus.