isaiah 54:1 Sing, O barren, thou that didst not bear; break forth into singing, and cry aloud, thou that didst not travail with child: for more are the children of the desolate than the children of the married wife, saith the LORD. - Free Bible Online

      Isa 54:1-17. THE FRUIT OF MESSIAH'S SUFFERINGS, AND OF ISRAEL'S FINAL PENITENCE AT HER PAST UNBELIEF (Isa 53:6): HER JOYFUL RESTORATION AND ENLARGEMENT BY JEHOVAH, WHOSE WRATH WAS MOMENTARY, BUT HIS KINDNESS EVERLASTING.

      Israel converted is compared to a wife (Isa 54:5; Isa 62:5) put away for unfaithfulness, but now forgiven and taken home again. The converted Gentiles are represented as a new progeny of the long-forsaken but now restored wife. The pre-eminence of the Hebrew Church as the mother Church of Christendom is the leading idea; the conversion of the Gentiles is mentioned only as part of her felicity [HORSLEY].

      1. Sing--for joy (Zep 3:14).
      barren--the Jewish Church once forsaken by God, and therefore during that time destitute of spiritual children (Isa 54:6).
      didst not bear--during the Babylonian exile primarily. Secondarily, and chiefly, during Israel's present dispersion.
      the children--the Gentiles adopted by special grace into the original Church (Isa 54:3; Isa 49:20, 21).
      than . . . married wife--than were her spiritual children, when Israel was still a married wife (under the law, before the Babylonian exile), before God put her away [MAURER]. So Paul contrasts the universal Church of the New Testament with the Church of the Old Testament legal dispensation, quoting this very passage (Ga 4:27). But the full accomplishment of it is yet future.

JFB.