Galatians 4:9, 25, 31

But now that you know God—or rather are known by God—how is it that you are turning back to those weak and miserable forces? Do you wish to be enslaved by them all over again?

Now Hagar stands for Mount Sinai in Arabia and corresponds to the present city of Jerusalem, because she is in slavery with her children.

Therefore, brothers and sisters, we are not children of the slave woman, but of the free woman.