isaiah 51:4 Hearken unto me, my people; and give ear unto me, O my nation: for a law shall proceed from me, and I will make my judgment to rest for a light of the people. - Free Bible Online

      4. my people--the Jews. This reading is better than that of GESENIUS: "O peoples . . . nations," namely, the Gentiles. The Jews are called on to hear and rejoice in the extension of the true religion to the nations; for, at the first preaching of the Gospel, as in the final age to come, it was from Jerusalem that the gospel law was, and is, to go forth (Isa 2:3).
      law . . . judgment--the gospel dispensation and institutions (Isa 42:1, "judgment").
      make . . . to rest--establish firmly; found.
      light, &c.-- (Isa 42:6).

JFB.