Romans 2:17

Ἰουδαῖος ἐπονομάζῃ : bearest the name of “Jew”. The ἐπὶ in the compound verb does not denote addition, but direction: Ἰουδαῖος is not conceived as a surname, but a name which has been imposed. Of course it is implied in the context that the name is an honourable one. It is not found in the LXX, and in other places where Paul wishes to indicate the same distinction, and the same pride in it, he says Ἰσραηλεῖται (Romans 9:4; 2 Corinthians 11:22). The terms must have had a tendency to coalesce in import, though Ἰουδαῖος is national, and Ἰσραηλείτης religious; for the religion was national. ἐπαναπαύη νόμῳ : grammatically νόμῳ is law; really, it is the Mosaic law. The Jew said, We have a law, and the mere possession of it gave him confidence. Cf. Micah 3:11, ἐπὶ τὸν Κύριον ἐπανεπαύοντο. καυχᾶσαι ἐν θεῷ : boastest in God, as the covenant God of the Jews, who are His peculiar people. καυχᾶσαι = καυχᾷ : the longer form is the usual one in the κοινή.