This is being said as an allegory, for these women represent two covenants. The one woman, Hagar, is from Mount Sinai, and her children are born into slavery.

Now Hagar is Mount Sinai in Arabia and corresponds to present-day Jerusalem, because she is in slavery along with her children.

But what does the Scripture say? "Drive out the slave woman and her son, for the son of the slave woman must never share the inheritance with the son of the free woman."