These things are said through an allegory. For these represent the two testaments. Certainly the one, on Mount Sinai, gives birth unto servitude, which is Hagar
Other versions
King James Version
Which things are an allegory: for these are the two covenants; the one from the mount Sinai, which gendereth to bondage, which is Agar. English Standard Version
Now this may be interpreted allegorically: these women are two covenants. One is from Mount Sinai, bearing children for slavery; she is Hagar.New International Version
These things may be taken figuratively, for the women represent two covenants. One covenant is from Mount Sinai and bears children who are to be slaves: This is Hagar.