Charles Spurgeon Commentary Isaiah 54:1-3

"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 Jehovah. Enlarge the place of thy tent, and let them stretch forth the curtains of thy habitations; spare not: lengthen thy cords, and strengthen thy stakes. For thou shalt spread aboard on the right hand and on the left; and thy seed shall possess the nations, and make the desolate cities to be inhabited." — Isaiah 54:1-3 (ASV)

Sing, O barren, you that did not bear; break forth into singing, and cry aloud, you that did not travail with child; for more are the children of the desolate than the children of the married wife, says the LORD. Enlarge the place of your tent, and let them stretch forth the curtains of your habitations: spare not, lengthen your cords, and strengthen your stakes; For you shall break forth on the right hand and on the left; and your seed shall inherit the Gentiles, and make the desolate cities to be inhabited.

Yet, they are called upon to praise God before the mercy comes.

Sing, O Barren, while still barren. Sing, O desolate one, while still desolate; and you who are narrowed and confined for space, thank God that he is about to enlarge you, and begin already to stretch your cords and strengthen your stakes.

We ought to act upon faith, and sing upon faith. The songs which are made at the sight of mercy are very sweet, but the songs that are sung before the mercy comes are those which are most acceptable to God.

We may say of the sonnets of faith, Blessed are they that have not seen and yet have believed.