i. e., The wisdom of the wise is seen in the words that issue from his lips; the folly of the fool is not only seen in his speech, but brings upon him the chastisement which he well deserves.

A rod is for the back of him - He that can learn, and will not learn, should be made to learn. The rod is a most powerful instrument of knowledge. Judiciously applied, there is a lesson of profound wisdom in every twig.

In the lips of him that hath understanding wisdom is found: but (g) a rod [is] for the back of him that is void of understanding.
(g) That is, God will find him out to punish him.

In the lips of him that hath understanding wisdom is found,.... He that has an understanding, especially of divine, spiritual, and evangelic things, which is the pure gift of God; wisdom will be found in his lips, his mouth will speak of it; not of mere natural wisdom, but spiritual wisdom; of the wisdom of God in his works; of Christ, the Wisdom of God; of the Gospel, the hidden wisdom; of inward experience of the grace of God, wisdom in the inward part, Psalm 37:30; from his lips will drop wise sayings, very instructive and informing; which those that seek for and observe may find to their profit and advantage, and to the great credit and honour of the understanding man; while the foolish man gets both stripes and disgrace, as follows;
but a rod is for the back of him that is void of understanding; or, "wants a heart" (e): that has no understanding of spiritual things in his heart, and so utters nothing but what is foolish and wicked, and, sooner or later, is chastised for it. The Septuagint, Syriac, and Arabic versions, read this clause in connection with the former, thus; "he that brings forth wisdom out of his lips smites with a rod him that is void of understanding".
(e) "carcutis corde"; Montanus, Mercerus, Gejerus.

Those that foolishly go on in wicked ways, prepare rods for themselves.

In the lips . . . found--hence, not beaten, as the wicked-speaking fool.
void of understanding-- (Proverbs 6:32; Proverbs 7:7).

There follow now two other proverbs on the use and abuse of speech:
On the lips of the man of understanding wisdom is found;
And the rod for the back of the fool.
With Lwenstein, Hitzig, and others, it is inadmissible to regard ושׁבט as a second subject to תּמּצא. The mouth itself, or the word of the mouth, may be called a rod, viz., a rod of correction (Isaiah 11:4); but that wisdom and such a rod are found on the lips of the wise would be a combination and a figure in bad taste. Thus 13b is a clause by itself, as Luther renders it: "but a rod belongs to the fool's back;" and this will express a contrast to 13a, that while wisdom is to be sought for on the lips of the man of understanding (cf. Malachi 2:7), a man devoid of understanding, on the contrary, gives himself to such hollow and corrupt talk, that in order to educate him to something better, if possible, the rod must be applied to his back; for, according to the Talmudic proverb: that which a wise man gains by a hint, a fool only obtains by a club. The rod is called שׁבט, from שׁבט, to be smooth, to go straight down (as the hair of the head); and the back גּו, from גּוה, to be rounded, i.e., concave or convex.

Wisdom - This wisdom shews itself in his speech. A rod - Rebukes from God and men.