54:1-3
Fred P Miller
[Verse 1: Rejoice: This verse is quoted in Gal. 4:27 and applied to the church which is the spiritual Israel and corresponds to heavenly Jerusalem or Zion. There is little doubt that the Apostles understood that the church of Christ is the fulfillment of the prophecies of the restoration of Zion under Messiah Jesus.

John Wesley
Sing - The prophet having largely discoursed of the sufferings of Christ, and of the blessed fruits thereof, and here foreseeing that glorious state of the church, he breaks forth into this song of triumph. And as the foregoing chapter literally speaks of Christ, so doth this of the church of Christ. This church, consisting at first of the Jews, and afterwards of the Gentiles, had been barren, 'till the coming of Christ. The desolate - The church of the Gentiles, which in the times of the Old Testament was desolate, does now bring forth to God a more numerous posterity than that of the Jews.

John Gill
V 54:1 "sing, O Jerusalem, which was a barren woman that bears not"
and so the apostle (Paul) applies the words of the text to the Jerusalem above, the mother of us all, the then present Gospel church, ( Galatians 4:26 Galatians 4:27 ) , which, at the first setting of it up, in the times of Christ, during his life and at the time of his death, and before the day of Pentecost, was like a barren woman; the number of converts were very small; few believed the report of the Gospel, professed Christ, and submitted to his ordinances; the names of the disciples were but a hundred and twenty. Though some understand this of the Jewish church, under the Old Testament dispensation, whose members were not many, and whose proselytes from the Gentiles were but few; and others of the Gentile world, before the coming of Christ, and the preaching of the Gospel in it; but the former sense is to be preferred, having the suffrage of the apostle
54:2 - To which the church is compared, because of its uncertain and movable condition, being sometimes in one place, and sometimes in another; and because of its outward meanness and weakness, as well as its small extent; but now it is signified that it should be enlarged, and room be made for an accession of in habitants to it; or, in other words, that the Gospel church state should not be confined to Jerusalem, but should take place in other parts of Judea, and in Galilee, and in Samaria; hence we read of churches in those places
Gill in his comments on 54:1-3 continue to write about the apostles spreading the church (movable as tents)
Throughout the world.

Matthew Poole
Ver. 2. Enlarge the place of thy tent, that it may be capable of the Gentiles, which shall flock to thee in great numbers, and desire to associate themselves with thee.
Let them, those to whom that work belongs, stretch forth. The meaning is, they must and shall be stretched out.
Lengthen thy cords, and strengthen thy stakes, that they may be able to support that great weight which the tents this enlarged shall be upon them
Ver. 3. Thou shalt break forth; thou shalt bring forth a multitude of children; for this word is commonly used of any great and extraordinary propagation of living creatures, whether beasts or men, Ge 30:30; Ex 1:12.
On the right hand and on the left; on every side, in all the parts of the world.
Thy seed; either,
1. Thy spiritual seed, the church of the new testament, which is accounted Abraham's seed, or children, Ga 3:7-9,29. Or,
2. Thy natural seed, Christ and his apostles, and other ministers, who were Jews, by whom this work was first and most eminently done. Shall inherit the Gentiles; shall subdue the Gentile world to the church, and to the obedience of the faith. The desolate cities; those cities and countries which in a spiritual sense were desolate and forsaken by God

Matthew Henry
INTRODUCTION TO ISAIAH CHAPTER 54
The death of Christ is the life of the church and of all that truly belong to it; and therefore very fitly, after the prophet had foretold the sufferings of Christ, he foretells the flourishing of the church, which is a part of his glory, and that exaltation of him which was the reward of his humiliation: it was promised him that he should see his seed, and this chapter is an explication of that promise. It may easily be granted that it has a primary reference to the welfare and prosperity of the Jewish church after their return out of Babylon, which (as other things that happened to them) was typical of the glorious liberty of the children of God, which through Christ we are brought into; yet it cannot be denied but that it has a further and principal reference to the gospel church, into which the Gentiles were to be admitted. And the first words being understood by the apostle Paul of the New-Testament Jerusalem (Ga 4:26-27) may serve as a key to the whole chapter and that which follows. It is here promised concerning the Christian church,

Geneva Study Bible
(a) After he has declared the death of Christ, he speaks to the Church, because it would feel the fruit of the same, and calls her barren, because in the captivity she was a widow without hope to have any children.
(b) The Church in this her affliction and captivity will bring forth more children, than when she was free, or this may be spoken by admiration, considering the great number that would come from her. Her deliverance under Cyrus was as her childhood, and therefore this was accomplished when she came of age, which was under the gospel.

[HORSLEY].
Israel converted is compared to a wife (Isa 54:5; 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

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

Adam Clarke
Verse 1. Sing, O barren, thou that didst not bear-"Shout for joy, O thou barren, that didst not bear"] The Church of God under the Old Testament, confined within the narrow bounds of the Jewish nation,

Other Comments
The desolate--the married wife; "the married wife" seems to be the ancient Jewish church in her union with God; "the desolate," the gentile church, which began with the rejection of the Jews, Ac 13:46-47; Ro 11:11-12,30; but with which the Jews are to be again unite

For next week : Isaiah 54, Galatians 4:21-31; Isaiah 30:1, 31:1: Jeremiah 3 (noting 1, 14, 19); Isaiah 10:20-22; Zechariah 14 (noting 16)