WPNT(i)
22 For it is written that Abraham had two sons: one by the slave woman and one by the free woman.
23 However, the one by the slave woman was born according to the flesh, while the one by the free woman was through the promise.
24 I will now allegorize them—these are two covenants: one is from Mount Sinai, bearing children into slavery, which is ‘Hagar’
25 (for this ‘Hagar’ is Mount Sinai in Arabia and corresponds to the present day Jerusalem, and is in slavery with her children);
26 while the ‘Jerusalem’ that is above is free, which is the mother of us all.
27 For it is written: “Rejoice, barren one, who does not give birth; break forth and shout, you who have no labor pains; because the abandoned woman has many more children than she who has the husband.”
28 Now we, brothers, like Isaac, are children of promise.
29 But, it is the same now as it was then: the one born according to flesh persecutes the one born according to Spirit.
30 However, what does the Scripture say? “Expel the slave woman and her son, because the son of the slave woman absolutely must not inherit with the son of the free woman!”
31 So then, brothers, we are not children of a slave woman, but of the free woman.