In Romans 2:18-20, what kind of knowledge did the Jewish religious leaders have because of the Mosaic law?
The Jewish religious leaders possessed the form of knowledge and truth contained in the Mosaic law. Being instructed out of that law, they knew God's will, approved the more excellent things, and considered themselves guides to the blind, lights in darkness, instructors of the foolish, and teachers of babes.
Les explains that Paul is addressing the Pharisees and other religious leaders of Israel, who were self-righteous and proud of their religious status. Because they were instructed out of the Mosaic law, they knew God's will and approved the things that are more excellent. They were confident they were a guide to the blind, a light to those in darkness, an instructor of the foolish, and a teacher of babes. They had the form of knowledge and the truth in the law. Yet Les points out that Paul immediately asks whether they taught themselves, exposing their hypocrisy: they were known for stealing from widows and the underprivileged, and Jesus overturned the money changers' tables because of their corrupt practices.
And knowest his will, and approvest the things that are more excellent, being instructed out of the law;
And art confident that thou thyself art a guide of the blind, a light of them which are in darkness,
An instructor of the foolish, a teacher of babes, which hast the form of knowledge and of the truth in the law.