Sing with gladness, etc. It is not stated who are addressed; but we may doubtless understand, from Isaiah 66:10, "all ye who love him," whether Jews or Gentiles. The latter, too, are interested in the restoration of Israel, because Israel is as it were a "priest" or mediator for the other nations (Isaiah 61:6).
Among the chief of the nations; rather, because of the chief of the nations. Israel is called the "chief of the nations" (so, with a cognate word for "chief," in Amos 6:1) because Jehovah has" chosen" it as his peculium (to use the language of the Vulgate), Deuteronomy 7:6, and because no other nation "hath God so nigh unto them," and "hath statutes and judgments so righteous," as Israel (Deuteronomy 4:7, Deuteronomy 4:8).