C. F. Keil and Franz Delitzsch on Proverbs 22:6

Pro 22:6 6 Give to the child instruction conformably to His way;    So he will not, when he becomes old, depart from it.

The first instruction is meant which, communicated to the child, should be על־פּי, after the measure (Gen 43:7 = post-bibl. לפי and כּפי) of his way, i.e., not: of his calling, which he must by and by enter upon (Bertheau, Zöckler), which דּרכּו of itself cannot mean; also not: of the way which he must keep in during life (Kidduschin 30a); nor: of his individual nature (Elster); but: of the nature of the child as such, for דּרך נער is the child’s way, as e.g., derek col-haarets, Gen 19:31, the general custom of the land; derek Mitsrâyim, Isa 10:24, the way (the manner of acting) of the Egyptians. The instruction of youth, the education of youth, ought to be conformed to the nature of youth; the matter of instruction, the manner of instruction, ought to regulate itself according to the stage of life, and its peculiarities; the method ought to be arranged according to the degree of development which the mental and bodily life of the youth has arrived at. The verb חנך is a denominative like עקב, Pro 22:4; it signifies to affect the taste, חך (= חנך), in the Arab. to put date syrup into the mouth of the suckling; so that we may compare with it the saying of Horace, Ep. i. 2, 69: Quo semel est imbuta recens servabit odorem Testa diu. In the post-bibl. Heb. חנּוּך denotes that which in the language of the Church is called catechizatio; חנוך (לנער) ספר is the usual title of the catechisms. It is the fundamental and first requisite of all educational instruction which the proverb formulates, a suitable motto for the lesson-books of pedagogues and catechists. ממּנּה [from it] refers to that training of youth, in conformity with his nature, which becomes a second nature, that which is imprinted, inbred, becomes accustomed. Pro 22:6 is wanting in the lxx; where it exists in MSS of the lxx, it is supplied from Theodotion; the Complut. translates independently from the Heb. text.