Galatians 4:21-31 - Hagar And Sarah Represent Two Covenants
21 Tell me, you who want to be subject to law, will you not listen to what the law says? 22 For the Scripture says that Abraham had two sons, one by a slave girl, the other by a free woman. 23 But the child of the slave girl was born in the ordinary course of nature, while the child of the free woman was born to fulfill the promise. 24 This is spoken as an allegory. For these women are two covenants, one coming from Mount Sinai, bearing children that are to be slaves; 25 that is, Hagar (and Hagar means Mount Sinai, in Arabia) and corresponds to the present Jerusalem, for Jerusalem is in slavery with her children. 26 But the Jerusalem that is above is free, and she is our mother. 27 For the Scripture says: "Rejoice, you childless woman, who never bore a child; break forth into shouting, you who feel no birth pangs; for the desolate woman has many children, even more than the married one."
28 Now we, brothers, like Isaac, are children born to fulfill the promise. 29 But just as then the child born in the ordinary course of nature persecuted the one born by the power of the Spirit, so it is today. 30 But what does the Scripture say? "Drive off the slave girl and her son, for the slave girl's son shall never share the inheritance with the son of the free woman."
31 So, brothers, we are children, not of a slave girl but of a free woman.