Albert Barnes 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)

Of the foolish. The word foolish is used in the Scriptures in two meanings—to denote those who are lacking understanding, and to denote the wicked. Here it is clearly used in the former sense, signifying that the Jew considered himself qualified to instruct those without knowledge.

Of babes. This is the literal meaning of the original word. The expression is figurative and denotes those who were as ignorant as children—an expression which they would be likely to apply to all the Gentiles. It is evident that the character here given by Paul to the Jews is one which they claimed and of which they were proud. They are often mentioned arrogating this prerogative to themselves, as being qualified to be guides and teachers of others (Matthew 14:14; Matthew 23:2, 16, 24).

It will be remembered, also, that the Jews considered themselves qualified to teach all the world and therefore showed great zeal to make proselytes. And it is not improbable (Tholuck) that their rabbis were accustomed to give the names "foolish" and "babes" to the ignorant proselytes whom they had made from the Gentiles.

Which hast the form of knowledge. The word here translated form properly denotes a delineation or picturing of a thing. It is commonly used to denote also the appearance of any object—that which we see, without reference to its internal character; the external figure. It sometimes denotes the external appearance as distinguished from that which is internal, or a hypocritical profession of religion without its reality, as in 2 Timothy 3:6: Having the form of godliness, but denying its power. It is sometimes used in a good and sometimes in a bad sense.

Here it denotes that in their teaching they retained the semblance, sketch, or outline of the true doctrines of the Old Testament. They had in the Scriptures a correct delineation of the truth. Truth is the representation of things as they are, and the doctrines which the Jews had in the Old Testament were a correct representation or delineation of the objects of knowledge (Compare to 2 Timothy 1:13).

In the law. That is, in the Scriptures of the Old Testament. In these verses, the apostle concedes to the Jews all that they would claim. Having made this concession of their superior knowledge, he is prepared with the more faithfulness and force to convict them of their deep and dreadful depravity in sinning against the superior light and privileges which God had conferred on them.