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.
Now Hagar stands for Mount Sinai in Arabia and corresponds to the present city of Jerusalem, because she is in slavery with her children.
But the Jerusalem that is above1 is free, and she is our mother.
References for Galatians 4:26