Charles Spurgeon Commentary Galatians 4:24

"Which things contain an allegory: for these [women] are two covenants; one from mount Sinai, bearing children unto bondage, which is Hagar." — Galatians 4:24 (ASV)

Which things are an allegory: for these are the two covenants: the one from the mount Sinai, which gendereth to bondage, which is Hagar.

Those who are under the law are the children, therefore, of the bondwoman: they are born slaves.