Paul turned his attention specifically to the Jews among the readers of his letter to believers in Rome.  But if¹ you call (ἐπονομάζῃ, a form of ἐπονομάζω) yourself a Jew (Ἰουδαῖος) and rely (ἐπαναπαύῃ, a form of ἐπαναπαύω) on the law² (νόμῳ, a form of νόμος) and boast (καυχᾶσαι, a form of καυχάομαι) of your relationship (ἐν, or boast in God) to God,³ he wrote, and know (γινώσκεις, a form of γινώσκω) his will (θέλημα) and approve (δοκιμάζεις, a form of δοκιμάζω) the superior things because you receive instruction (κατηχούμενος, a form of κατηχέω) from the law (νόμου, another form of νόμος)…⁴

This all sounds like pretty good stuff to me.  Since I’ve read Paul so many times before I’m a bit suspicious of relying or resting (ἐπαναπαύῃ) on the law.  I have encountered the word καυχάομαι enough to know that boast of your relationship to God was the translators’ choice.  It might have been translated rejoice.⁵  All in all this sounds like a description of one who would do (ποιῶσιν, a form of ποιέω; Addendum below) the law (νόμου, another form of νόμος).  Since I know the proverb—Pride goes before destruction, and a haughty spirit before a fall⁶—and have a feel for its use in storytelling, I get more suspicious as Paul continued (Romans 2:19, 20 NET).

…and if you are convinced (πέποιθας, a form of πείθω) that you yourself are a guide to the blind, a light to those who are in darkness, an educator of the senseless, a teacher of little children, because you have in the law (νόμῳ, a form of νόμος) the essential features of knowledge (γνώσεως, a form of γνῶσις) and of the truth (ἀληθείας, a form of ἀλήθεια)…

Without ever using the word ὑποκριτής (actor) Paul presented a classic definition: therefore you who teach someone else, do you not teach yourself?  You who preach against stealing, do you steal?  You who tell others not to commit adultery, do you commit adultery?  You who abhor idols, do you rob temples?⁷ I think Paul singled out the Jews here because he knew himself and his own people best.  He hadn’t been to Rome to meet the Romans yet.  Sometimes I feel like there are really only two types of people in the world, hypocrites and those who don’t even try.

When I think like that, however, I am defining hypocrite as a person who does not fully practice what he preaches or believes or aspires to.  Obviously I have just described everyone who preaches, believes or aspires to anything.  Paul was more specific.  His definition was one who relies or rests on God’s law, perhaps more to the point, one who relies or rests on his own ability to keep God’s law and then does not fully practice the law he preaches, believes and aspires to.

You who boast (καυχᾶσαι, a form of καυχάομαι) in the law (νόμῳ, a form of νόμος), Paul continued, dishonor (ἀτιμάζεις, a form of ἀτιμάζω) God by transgressing (παραβάσεως, a form of παράβασις) the law (νόμου, another form of νόμος)!  For just as it is written, “the name of God is being blasphemed among the Gentiles because of you.”⁸  Paul’s quotation here from Isaiah 52:5 [Table] is not simply a matter of piling on, of kicking the Jews who relied on, and didn’t fully live up to, the law when they were down.  It’s a flashing beacon of the mind of Christ and a portent where Paul’s thoughts, and letter, were headed.

This boasting in the law, this dishonoring of God by transgressing the law, was known.  It was prophesied.  It is part of God’s Holy Word.  It was like Jesus prophesying to Peter, I tell you the truth, on this night, before the rooster crows, you will deny me three times,⁹ but on a grander scale.  Here is the promise that follows Isaiah 52:5 (Isaiah 52:6-12 NET):

For this reason my people will know my name, for this reason they will know at that time that I am the one who says, “Here I am.”  How delightful it is to see approaching over the mountains the feet of a messenger who announces peace, a messenger who brings good news, who announces deliverance, who says to Zion, “Your God reigns!”  Listen, your watchmen shout; in unison they shout for joy, for they see with their very own eyes the Lord’s return to Zion.  In unison give a joyful shout, O ruins of Jerusalem!  For the Lord consoles his people; he protects Jerusalem.  The Lord reveals his royal power in the sight of all the nations; the entire earth sees our God deliver.  Leave!  Leave!  Get out of there! Don’t touch anything unclean!  Get out of it!  Stay pure, you who carry the Lord’s holy items!  Yet do not depart quickly or leave in a panic.  For the Lord goes before you; the God of Israel is your rear guard.

Addendum: November 1, 2020
In the second paragraph I had indicated that ποιῶσιν was a form of ποιητής.  It is actually a form of ποιέω.  I may have been thinking of Romans 2:13 where do was the NET translation of ποιηταὶ which is a form of ποιητής.

A table of Isaiah 52:6-12 translated from the Masoretic text and the Septuagint follows:

Tables comparing Proverbs 16:18; Isaiah 52:6; 52:7; 52:8; 52:9; 52:10; 52:11 and 52:12 in the Tanakh, KJV and NET, and Proverbs 16:18; Isaiah 52:6; 52:7; 52:8; 52:9; 52:10; 52:11 and 52:12 in the Septuagint (BLB and Elpenor) follow.  Following those is a table comparing Romans 2:17 in the NET and KJV.