Galatians 4:25

4:25 Now Hagar represents Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children.

Galatians 4:30

4:30 But what does the scripture say? “Throw out the slave woman and her son, for the son of the slave woman will not share the inheritance with the son” ¹  of the free woman.

[4:30]  ¹ sn A quotation from Gen 21:10. The phrase of the free woman does not occur in Gen 21:10.