Romans 2:20

Instructor. Or, “corrector.” The Greek word combines the senses of both teaching and discipline.

Babes. That is, religiously immature persons. The Jews so regarded Gentile proselytes to Judaism. Jesus used the term to refer to the common people who heard Him gladly (Matt. 11:25). Paul thus described the new Corinthian converts (1 Cor. 3:1).

Form. Gr. morphosis, “a form,” “an outline,” “a semblance.” Paul is referring to the outline without the substance. The only other occurrence of this word in the NT is in 2 Tim. 3:5, where the “form of godliness” is contrasted with the “power thereof.” In Romans, Paul is speaking of the outline, framework, embodiment, of knowledge and truth that the Jews had available in the law. God had designed that this “form” not only should be a guide to the Jews but should in turn be used by them to teach the truths of the gospel to the Gentiles.

In the law. Perhaps a general reference to the teachings of the OT as a whole (see on v. 12).