Hagar and Sarah Represent Two Covenants

21 Tell me, [you] who are wanting to be under the law, do you not understand the law?
22 For it is written that Abraham had two sons, one by the female slave and one by the free woman.
23 But the one by the female slave was born according to human descent, and the one by the free woman through the promise,
24 which [things] are spoken allegorically, for these [women] are two covenants, one from Mount Sinai, bearing [children] for slavery, who is Hagar.
25 Now Hagar is Mount Sinai in Arabia, and corresponds to the present Jerusalem, for she is a slave with her children.
26 But the Jerusalem above is free, which is our mother.
27 For it is written, "Rejoice, O barren woman, who does not give birth to [children]; burst out and shout, [you] who do not have birth pains, because many [are] the children of the desolate [woman], even more than [those of] the one who has a husband."
28 But you, brothers, are children of the promise, just as Isaac.
29 But just as at that time the [child] born according to human descent persecuted the [child born] according to the Spirit, so also now.
30 But what does the scripture say? "Drive out the female slave and her son, for the son of the female slave will never inherit with the son" of the free woman.
31 Therefore, brothers, we are not children of the female slave but of the free woman.