Galatians 4:21-31 - Hagar And Sarah Represent Two Covenants
21 Tell me, you that desire to be under the law, do you not listen to the law? 22 For it is written that Abraham had two sons, one by the handmaid, and one by the free woman. 23 However, the son by the handmaid was born according to the flesh, but the son by the free woman was born through promise. 24 These things contain an allegory, for these are two covenants. One is from Mount Sinai, bearing children to slavery, which is Hagar. 25 For this Hagar is Mount Sinai in Arabia, and represents Jerusalem that exists now, for she is in slavery with her children. 26 But the Jerusalem that is above is free, and she is our mother. 27 For it is written, "Rejoice, you barren who do not bear. Break forth and shout, you that do not travail. For more are the children of the desolate than of her who has a husband."
28 Now you, brothers, as Isaac was, are children of promise. 29 But as then, he who was born according to the flesh persecuted him who was born according to the Spirit, so also it is now. 30 However what does the Scripture say? "Throw out the handmaid and her son, for the son of the handmaid will not inherit with the son of the free woman."
31 So then, brothers, we are not children of a handmaid, but of the free woman.