An instructor of the foolish,.... All men in a state of unregeneracy are foolish, and need instruction; here the common people among the Jews, who knew not the law, are meant; it was very usual to call anyone of their doctors and masters hrwm, "an instructor": it follows,a teacher of babes; either in age or in understanding; such who taught either of them were called by the Jews twqwnyt ydmlm, "teachers of babes".
Thus they paraphrase the text in Da 12:3:"they that be wise, shall shine as the brightness of the firmament. This is the Judge who judges, the judgment of truth truly, and the collectors of alms: and they that turn, many to righteousness, as the stars for ever and ever; these are, twqwnt ydmlm, "the teachers of babes" .'
'Though these are said to be inferior to the wise men, or doctors:which hast the form of knowledge, and of the truth in the law: they had not a true knowledge of the law; only a draught and scheme, the outward form of the law, and a mere shadow and appearance of the knowledge of the truth of it.
From hence the apostle would have it concluded, that though the Jews had the law, and in some sense knew it, yet inasmuch as they did not perform it, they could not be justified by it; and that even their teachers, their greatest masters and doctors, were very deficient, as appears from what follows; and since they could not be instilled by it, who taught others the knowledge of it, the hearers of it could not expect justification from it.
T. Bab. Bava Bathra, fol. 8. 2. & 21. 1, 2. Maimon. Hilchot Talmud Tora, c. 2. sect. 1. Gloss in Sota, fol. 49.