C. F. Keil and Franz Delitzsch on Proverbs 10:14

Pro 10:14 14 Wise men store up knowledge;      But the mouth of the fool is threatening destruction.

Ewald, Bertheau, Hitzig, Oetinger: “The mouth of the fool blunders out, and is as the sudden falling in of a house which one cannot escape from.” But since מחתּה is a favourite Mishle-word to denote the effect and issue of that which is dangerous and destructive, so the sense is perhaps further to be extended: the mouth of the fool is for himself (Pro 13:3) and others a near, i.e., an always threatening and unexpectedly occurring calamity; unexpectedly, because suddenly he blunders out with his inconsiderate shame-bringing talk, so that such a fool’s mouth is to every one a praesens periculum. As to יצפּנוּ, it is worthy of remark that in the Beduin, Arab. dfn, fut. i, signifies to be still, to be thoughtful, to be absorbed in oneself (vid., Wetstein on Job, p. 281). According to Codd. and editions, in this correct, וּפי־ is to be written instead of אויל uwpiy; vid., Baer’s Torath Emeth, p. 40.