21 Tell me, ye who are willing to be under law, the law do ye not hear? 22 for it hath been written, that Abraham had two sons, one by the maid-servant, and one by the free-woman, 23 but he who 'is' of the maid-servant, according to flesh hath been, and he who 'is' of the free-woman, through the promise; 24 which things are allegorized, for these are the two covenants: one, indeed, from mount Sinai, to servitude bringing forth, which is Hagar; 25 for this Hagar is mount Sinai in Arabia, and doth correspond to the Jerusalem that now 'is', and is in servitude with her children, 26 and the Jerusalem above is the free-woman, which is mother of us all, 27 for it hath been written, 'Rejoice, O barren, who art not bearing; break forth and cry, thou who art not travailing, because many 'are' the children of the desolate—more than of her having the husband.'
Matthew Henry's Commentary on Galatians 4:21-27
Commentary on Galatians 4:21-27
(Read Galatians 4:21-27)
The difference between believers who rested in Christ only, and those who trusted in the law, is explained by the histories of Isaac and Ishmael. These things are an allegory, wherein, beside the literal and historical sense of the words, the Spirit of God points out something further. Hagar and Sarah were apt emblems of the two different dispensations of the covenant. The heavenly Jerusalem, the true church from above, represented by Sarah, is in a state of freedom, and is the mother of all believers, who are born of the Holy Spirit. They were by regeneration and true faith, made a part of the true seed of Abraham, according to the promise made to him.