The way of transgressors is hard - Never was a truer saying; most sinners have more pain and difficulty to get their souls damned, than the righteous have, with all their cross-bearings, to get to the kingdom of heaven.

Every prudent man dealeth with knowledge,.... In order to get more, and with men of knowledge for the same purpose; all he does is with knowledge and discretion; he does not meddle with things, nor has he to do with persons, he knows nothing of; he both acts and speaks with knowledge, cautiously, wisely, considering well time, place, and persons: and every wise and good man deals with evangelical knowledge, and studies to grow in the knowledge of the Gospel, and the mysteries of it; in the knowledge of Christ, and of God in Christ; the issue of which is life eternal;
but a fool layeth open his folly; or "spreads" (q) it; and exposes it to the view of everyone, by his foolish talk and indiscreet actions.
(q) "expandit", Mercerus, Gejerus, Michaelis.

It is folly to talk of things of which we know nothing, and to undertake what we are no way fit for.

dealeth--acts with foresight.
a fool . . . folly--for want of caution.

16 Every prudent man acteth with understanding;
But a fool spreadeth abroad folly.
Hitzig reads, with the Syr. (but not the Targ.) and Jerome, כּל (omnia agit), but contrary to the Hebr. syntax. The כּל־ is not feeble and useless, but means that he always acts בּדּעת, mit Bedacht [with judgment] (opp. בּבלי דעת, inconsulto, Deuteronomy 4:42; Deuteronomy 19:4), while on the contrary the fool displays folly. Proverbs 12:23 and Proverbs 15:2 serve to explain both members of the verse. Bedchtigkeit [judgment] is just knowledge directed to a definite practical end, a clear thought concentrated on a definite point. יקרא, he calls out, and יבּיע, he sputters out, are parallels to יפרשׂ. Fleischer: פּרשׂ, expandit (opp. Arab. ṭawy, intra animum cohibuit), as a cloth or paper folded or rolled together, cf. Schiller's
(Note: "Er breitet es heiter und glnzend aus,
Das zusammengewickelte Leben.") -
"He spreads out brightly and splendidly
The enveloped life."
There lies in the word something derisive: as the merchant unrolls and spreads out his wares in order to commend them, so the fool does with his foolery, which he had enveloped, i.e., had the greatest interest to keep concealed within himself - he is puffed up therewith.

Knowledge - Considerately and discreetly. Layeth open - By his foolish actions.