Romans 15:10 - Ellicott's Commentary On The Whole Bible

Rejoice, ye Gentiles, with his people — St. Paul here follows the LXX. version, which varies somewhat from the original. The sense of the Hebrew is disputed. That which appears to suit the context best — “Rejoice, O ye nations of His people,” i.e., the Jewish tribes — is questioned on the ground of linguistic usage. In place of this, we may either adopt the rendering of the Vulgate — “Ye nations (Gentiles) praise His people,” or, “Rejoice, ye nations (Gentiles), who are His people.” This, however, hardly seems to fall in with the context so well.