Adam Clarke on Galatians 4:27

Rejoice, thou barren that bearest not - This quotation is taken from Isa 54:1, and is certainly a promise which relates to the conversion of the Gentiles, as the following clause proves; for the desolate - the Gentile world, hath many more children - is a much larger and more numerous Church, than she - Jerusalem, the Jewish state, which hath a husband - has been so long in covenant with God, living under his continual protection, and in possession of a great variety of spiritual advantages; and especially those offered to her by the Gospel, which she has rejected, and which the Gentiles have accepted.