Brutish - Dumb as a brute beast. The difference between man and brute lies chiefly in the capacity of the former for progress and improvement, and that capacity depends upon his willingness to submit to discipline and education. Compare Psalm 49:12.

Whoso loveth instruction - מוסר musar, discipline or correction, loves knowledge; for correction is the way to knowledge.
But he that hateth reproof is brutish - בער baar, he is a bear; and expects no more benefit from correction than the ox does from the goad.

Whose loveth instruction loveth knowledge,.... That loves the instruction of Wisdom, or Christ, Proverbs 4:13; the means of instruction, the Scriptures, which are profitable for instruction in righteousness, and are written for our learning; the Gospel, which instructs into the person, office, and grace of Christ; the ministers of the word, who are so many instructors in Christ; and even the rod of afflictions, by which men are taught their duty, and the will of God: and these are to be loved; and he that loves them clearly shows that he loves knowledge; since the means of instruction, making use of them, and getting instruction by them, are attended with labour, trouble, and difficulty; which a man would not choose, had he not a love unto and a desire after knowledge, and an increase of it; as the knowledge of God, of Christ, and of his truths. Aben Ezra inverts the words;
"he that loves knowledge loves instruction;''
but the sense is much the same;
but he that hateth reproof is brutish; or a "beast" (k): as the man that is willing to be instructed, in order to gain knowledge, shows himself to be a wise and understanding man; so he that hates the reproof the word of God gives, or the ministers of it, or God by them, appears to be no better than a brute, than the horse or mule that want understanding: so the man of sin hates the Scriptures, the Gospel, and the ministers of it, and the reproofs and convictions they give of his idolatry, superstition, and will worship; nor does he care that his doctrines and practices should be brought to this test, or that the people should have knowledge of them; but keeps them from them, and sets up his own infallibility as the rule of judgment; and it is one character of his followers, that they "receive not the love of the truth", 2-Thessalonians 2:10; and both he and they are represented by a beast, Revelation 13:1; and are more brutish than any man; see Proverbs 5:11.
(k) "instar bruti indocilis est", Michaelis.

Those who have grace, will delight in the instructions given them. Those that stifle their convictions, are like brutes.

(Proverbs. 12:1-28)
loveth knowledge--as the fruit of instruction or training (Proverbs 1:2).
hateth reproof-- (Proverbs 10:17).
brutish--stupid, regardless of his own welfare (Psalm 49:10; Psalm 73:22).

Three proverbs on knowledge, the favour of God, firmness and the means thereto.
1 He loveth correction who loveth knowledge,
And he hateth instruction who is without reason.
It is difficult in such cases to say which is the relation of the ideas that is intended. The sequence of words which lies nearest in the Semitic substantival clause is that in which the predicate is placed first; but the subject may, if it is to be made prominent, stand at the head of the sentence. Here, 1b, the placing of the subject in advance recommends itself: one who hates instruction is devoid of reason. But since we have no reason in 1a to invert the order of the words as they lie together, we take the conceptions placed first in both cases as the predicates. Thus: he who loves knowledge shows and proves that he does so by this, that he willingly puts himself in the place of a learner; and devoid of reason is he who with aversion rejects reproof, which is designed to guard him from future mistakes and false steps. Regarding the punctuation דעת אהב (with Mercha on the ante-penult. and the העמדה-sign on the penult.), vid., at Proverbs 11:26., Proverbs 1:19. In 1b the Munach in תוכחת is transformed from Mugrash (Accentssystem, xviii. 2), as in Proverbs 15:10. בּער (cf. Proverbs 30:2) is a being who is stupid as the brute cattle (בּעיר, from בּער, to graze, cattle of all kinds; Arab. b'ayr, the beast κατ ̓ ἐξ., i.e., the camel); as a homo brutus is compared to a בּהמּה (Ps. 49:21), 73:22), and is called Arab. behymt, from bahym, "shut up" (spec. dabb, a bear; thwr, an ox; ḥamâr, an ass) (Fl.).