A.T. Robertson Commentary Romans 2:20

"a corrector of the foolish, a teacher of babes, having in the law the form of knowledge and of the truth;" — Romans 2:20 (ASV)

A corrector of the foolish (παιδευτην αφρονων). Old word (from παιδευω) for instructor, in Plato, and probably so here, though corrector or chastiser in Heb 12:9 (the only N.T. instances). See Lu 23:16. Late inscriptions give it as instructor (Preisigke). Αφρονων is a hard word for Gentiles, but it is the Jewish standpoint that Paul gives. Each termed the other "dogs."

Of babes (νηπιων). Novitiates or proselytes to Judaism just as in Ga 4:1. Paul used it of those not of legal age.

The form (την μορφωσιν). Rare word only in Theophrastus and Paul (here and 2 Timothy 3:5). Pallis regards it as a Stoical term for education. Lightfoot considers the μορφωσις as "the rough-sketch, the pencilling of the μορφη," the outline or framework, and in 2 Timothy 3:5 "the outline without the substance." This is Paul's picture of the Jew as he sees himself drawn with consummate skill and subtle irony.