| Gill's Exposition of the Entire Bible A fool's mouth is his destruction,.... The cause of it; for his contentions, and quarrels, and evil speaking, lawsuits are commenced against him, which bring ruin upon himself and his family now; as well as for his idle and wicked words he will be condemned hereafter, Matthew 12:35; there is a world of iniquity in the mouth and tongue of a wicked man, which bring destruction upon himself and others, James 3:6; and his lips are the snare of his soul; from speaking in his own defence, he says things which should not be said, and by which he is entangled yet more and more; he is caught by his own words and condemned by them; or his loquacity, in which he delights, is a snare unto him to say things which neither become him, nor are for his advantage, but the contrary; see Proverbs 12:13.
Keil and Delitzsch Biblical Commentary on the Old Testament7 The mouth of the fool is to him destruction, And his lips are a snare to his soul. As Proverbs 18:6 corresponds to Proverbs 17:27 of the foregoing group, so this Proverbs 18:7 corresponds to Proverbs 17:28. Regarding מחתּה־לּו, vid., Proverbs 13:3. Instead of פי כּסיל, is to be written פּי־כסיל, according to Torath Emeth, p. 40, Cod. 1294, and old editions.
Geneva Study BibleA fool's mouth is his destruction, and his lips are the snare of his soul.
Matthew Henry's Concise Commentary18:4. The well-spring of wisdom in the heart of a believer, continually supplies words of wisdom. 5. The merits of a cause must be looked to, not the person. 6,7. What mischief bad men do to themselves by their ungoverned tongues! 8. How base are those that sow contention! and what fatal effects may be expected from small beginnings of jealousy! 9. Omissions of duty, and in duty, are fatal to the soul, as well as commissions of sin. 10,11. The Divine power, made known in and through our Lord Jesus Christ, forms a strong tower for the believer, who relies on the Lord. How deceitful the defence of the rich man, who has his portion and treasure in this world! It is a strong city and a high wall only in his own conceit; for it will fail when most in need. They will be exposed to the just wrath of that Judge whom they despised as a Saviour. 12. After the heart has been lifted up with pride, a fall comes. But honour shall be the reward of humility. 13. Eagerness, with self-conceit, will expose to shame. 14. Firmness of mind supports under many pains and trials. But when the conscience is tortured with remorse, no human fortitude can bear the misery; what then will hell be? 15. We must get knowledge, not only into our heads, but into our hearts. 16. Blessed be the Lord, who makes us welcome to come to his throne, without money and without price. May his gifts make room for him in our souls. | 
