Indeed you are called a Jew, and rest on the law, and make your boast in God, and know his will, and approve the things that are excellent, being instructed out of the law, and are confident that you yourself are a guide to the blind, a light to those who are in darkness, an instructor of the foolish, a teacher of babes, having the form of knowledge and truth in the law.
In the first chapter Paul had shown that the heathen were lost because of their idolatry and immorality. Then he had addressed those of the heathen or Jews who considered themselves “decent”. Now he starts to invalidate further objections the Jews had of the gospel.
The Jews had indeed received many privileges from God; this Paul acknowledges. The term “Jew” was the epitome of those privileges (cf. Romans 3:1; 9:3-5). They had the law and knew the one true God. Nor were they ignorant as to God’s will. They understood what was “excellent” and agreed with it.
God had entrusted the Jews with “the form of knowledge and truth”. And what had they done with it? If they were the ones to whom God had revealed truth and knowledge, then it was their duty to live accordingly and do His will. Did the Jews encourage each other to carry out God’s will? Not at all! Yet they imagined they could teach the “blind and foolish” heathen. In verses 21-23 Paul continues the accusation he began with “You are called a Jew” in verse 17. There he brings to light the contradiction in their moral conduct.
Image: By Valentin de Boulogne – Blaffer Foundation Collection, Houston, TX, Public Domain, https://commons.wikimedia.org/w/index.php?curid=596565