Galatians 4:21-31 - Hagar And Sarah Represent Two Covenants
21 Tell me, those of you who desire to be under [obligation to the requirements of] the law of Moses: Are you really paying attention to what the law of Moses says? 22 For it is written in the law about Abraham's two sons [Gen. 16]; one [was] by his slave woman [Hagar] and the other by the free woman, [his wife, Sarah]. 23 Now the son [Ishmael], born to the slave woman, was born simply of their natural relationship; but the son [Isaac], born to the free woman, was born in fulfillment of a [divine] promise. 24 This set of circumstances contains an illustration; for these two women [Hagar and Sarah] represent the two Agreements [between God and mankind]. The one [Agreement], given at Mount Sinai, represents Hagar, whose children became [the Israelites], enslaved under bondage [to the requirements of the law of Moses]. 25 Now this woman, Hagar, is similar to Mount Sinai, in Arabia, and represents the present [earthly] Jerusalem [i.e., Israel], consisting of children in bondage [to the law of Moses]. 26 But the heavenly Jerusalem [Heb. 12:22] consists of free people, and is the mother of us [Christians]. 27 For it is written [Isa. 40:1], "[Woman] you should be happy that you have not had children. Cry over your inability to experience the pain of childbirth. For the deserted woman has had more children than the one with a husband."
28 Now, brothers, you [Christians] are children of the promise [made to Abraham. See 3:29] just like Isaac, [Abraham's son] was. 29 But, just as it was then --- the son born in the ordinary way [i.e., Ishmael] persecuting the one born according to the Holy Spirit's [leading, i.e., Isaac] --- so it is now [i.e., Jews urging compliance with the requirements of the law of Moses persecuting those who refuse to return to dependance on that law for salvation. See 3:1-3]. 30 What does the Scripture say about this matter? [It says, Gen. 21:10-12], "Get rid of the slave woman [Hagar], with her son [Ishmael]; for the son of the slave woman [Ishmael] will not inherit [what God promised to Abraham and his descendants], along with the son of the free woman [i.e., Isaac]."
31 Therefore, brothers, we [Christians] are not the [spiritual] children of the slave woman [Hagar] but of the free woman [Sarah].