חֲנֹ֣ךְ לַ֭נַּעַר עַל־פִּ֣י דַרְכּ֑וֹ גַּ֥ם כִּֽי־יַ֝זְקִ֗ין לֹֽא־יָס֥וּר מִמֶּֽנָּה׃
Train up a child in the way he should go, And even when he is old, he will not depart from it.
Rashi on Proverbs
Train a child According to what you teach a child and train him in matters, either for good or bad, even when he grows old, he will not turn away from it.
Metzudat David on Proverbs
Start to accustom the boy in his [early] years to the service of God through wisdom in things small and big; once he is accustomed to serving God well, when he grows old he will not stray [from the path] because his deeds will be enlightened.