The heart of him that hath understanding seeketh knowledge,.... He that has in his heart an understanding of divine and spiritual things, of the Gospel and of the truths of it, will seek earnestly and diligently in the use of proper means after more knowledge; as he will desire to know more of Christ, his person, offices, and grace, he will follow on to know him, and not be content with the present degree of knowledge he has attained unto; he will hear and read the word, and pray and meditate, in order to come to a more perfect knowledge of the son of God, and of those things which relate to his spiritual peace and eternal welfare;
but the mouth of fools feedeth on foolishness; on foolish talking and jesting; on foolish and unlearned questions; on foolish and false doctrines; on foolish and hurtful lusts; on wind and ashes, a deceived heart having turned them aside: they take pleasure and satisfaction in those things; feed their fancy with them and feast upon them, which shows what fools they are; and such all unregenerate men be.

A wise man seeks to gain more wisdom, growing in grace and in the knowledge of Christ. But a carnal mind rests contented, flattering itself.

(Compare Proverbs 10:21-22). The wise grow wiser, the fools more foolish (Proverbs 9:9).

14 The heart of the understanding seeketh after knowledge,
And the mouth of fools practiseth folly.
Luther interprets רעה as metaphor. for to govern, but with such ethical conceptions it is metaphor. for to be urgently circumspect about anything (vid., Proverbs 13:20), like Arab. ra'y and r'âyt, intentional, careful, concern about anything. No right translation can be made of the Chethib פני, which Schultens, Hitzig, Ewald, and Zckler prefer; the predicate can go before the פּני, after the Semitic rule in the fem. of the sing., 2-Samuel 10:9, cf. Job 16:16, Chethib, but cannot follow in the masc. of the sing.; besides, the operations of his look and aspect are ascribed to his face, but not spiritual functions as here, much more to the mouth, i.e., to the spirit speaking through it. The heart is within a man, and the mouth without; and while the former gives and takes, the latter is always only giving out. In Proverbs 18:15, where a synonymous distich is formed from the antithetic distich, the ear, as hearing, is mentioned along with the heart as appropriating. נבון is not an adj., but is gen., like צדיק, 28a (opp. ופי). חכם, Proverbs 16:23. The φιλοσοφία of the understanding is placed over against the μωρολογία of the fools. The lxx translates καρδία ὀρθὴ ζητεῖ αἲσθησιν (cf. Proverbs 14:10, καρδία ἀδρὸς αἰσθητική); it uses this word after the Hellenistic usus loq. for דעת, of experimental knowledge.

Foolishness - Wickedness is meat and drink to them.