Εἰ δὲ σὺ Ἰουδαῖος ἐπονομάζῃ: a condition without an apodosis

Says 2:17–20 is a chain of conditions: εἰ δὲ σὺ Ἰουδαῖος ἐπονομάζῃ καὶ ἐπαναπαύῃ νόμῳ καὶ καυχᾶσαι ἐν θεῷ καὶ γινώσκεις τὸ θέλημα … πέποιθάς τε σεαυτὸν ὁδηγὸν εἶναι τυφλῶν. No main clause follows. At 2:21 a fresh start with resumptive οὖν (ὁ οὖν διδάσκων ἕτερον σεαυτὸν οὐ διδάσκεις;) takes its place: a series of questions. SBLGNT marks the break with a dash after 2:20. The BSB repeats "if" and begins 2:21 "you, then." The Byzantine Ἴδε ("look") removes the break (var.Rom.2.17.ei-de-ide).

Says ἐπονομάζῃ is passive, "you are called" (BSB "call yourself"); Abbott-Smith gives "to name, call by a name, surname." ἐπαναπαύῃ νόμῳ is "you rest upon the law" (Abbott-Smith, middle: "to rest upon"). Swete's LXX of Mic 3:11 uses the same verb of corrupt leaders who claim security: καὶ ἐπὶ τὸν κύριον ἐπανεπαύοντο λέγοντες Οὐχὶ Κύριος ἐν ἡμῖν ἐστιν;

Implies καυχᾶσαι ἐν θεῷ and γινώσκεις τὸ θέλημα probably recall Jer 9:23–24 (MT 9:22–23), which shares καυχάομαι ἐν, γινώσκω and θέλημα; Mic 3:11 shares only the verb (ἐπανεπαύοντο; 2:17 ἐπαναπαύῃ νόμῳ, without ἐπί).

Says Swete reads μὴ καυχάσθω ὁ σοφὸς ἐν τῇ σοφίᾳ αὐτοῦ … ἀλλ᾽ ἢ ἐν τούτῳ καυχάσθω ὁ καυχώμενος, συνίειν καὶ γινώσκειν ὅτι ἐγώ εἰμι Κύριος, ending ὅτι ἐν τούτοις τὸ θέλημά μου.

Implies The privileges are real (compare 3:1–2; 9:4) and are listed in Paul's own terms. The broken sentence turns them into the ground of an accusation: the one who relies on the law and boasts in God is asked whether he keeps it (2:21–23).