These things serve as illustrations, for the women represent two covenants. One covenant is from Mount Sinai and bears children into slavery: This is Hagar.
24. These are the two covenants. I have thought it better to adopt this translation, in order not to lose sight of the beauty of the comparison; for Paul compares the two διαθὢκαι, to two mothers, and to employ testamentum, (a testament,) which is a neuter noun, for denoting a mother, would be harsh.
In these verses the apostle illustrates the difference between believers who rested in Christ only and those judaizers who trusted in the law, by a comparison taken from the story of Isaac and Ishmael. This he introduces in such a manner as was proper to strike and impress their minds, and to convince them of their great weakness in departing from the truth, and suffering...
Commenting on Galatians 4:21-31
For this Agar is Mount Sinai in Arabia,.... The Arabic version, instead of Arabia, reads "Balca". The Syriac version makes Hagar to be a mountain, reading the words thus, "for Mount Hagar is Sinai, which is in Arabia": and some have been of opinion that Sinai was called Hagar by the Arabians.