Tell me, you who desire to be under the law, do you not listen to the law? For it is written that Abraham had two sons, one by a slave woman and one by a free woman. But the son of the slave was born according to the flesh, while the son of the free woman was born through promise. Now this may be interpreted allegorically: these women are two covenants. One is from Mount Sinai, bearing children for slavery; she is Hagar. Now Hagar is Mount Sinai in Arabia; she corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free, and she is our mother. For it is written,
“Rejoice, O barren one who does not bear;
break forth and cry aloud, you who are not in labor!
For the children of the desolate one will be more
than those of the one who has a husband.”
Comment: The story of Abraham and his first two sons is historical. Historically one (Isaac) was born according to the promise of God. One (Ishmael) was born because feeling herself incapable of bearing a child Sarah gave Hagar, her maid, to her husband and thought that she was thereby fulfilling God’s promise. Paul in this allegorical meaning of the historical truth sees Isaac as being born according to God’s promise and the representative of those who are attached to eternal truth (the New Jerusalem from above); whereas Ishmael is tied to Mount Sinai and its laws as seen in obedience to the law (the earthly Jerusalem). His quote from Isaiah 54 v1, just after Is 53 with its prediction of the saving death of Christ, sees Sarah as rejoicing in those born through the Isaac line of promise!
Prayer: Thank You for Christ as the fulfilment of Your promise to Abraham!
As I read it! 
Thank you Barry for your comments on this passage. When Paul writes the story of Abraham and Sarah, and the birth of Ishmael and then Isaac, the son of the promise, it makes it all sound fundamentally good. But I think, if I were Sarah, having to wait such a long time for God’s promise to be fulfilled, I think I would probably have done the same thing that she did in giving Abraham to her slave, Hagar, because humanly it was impossible for Sarah to conceive and bear a child. We humans find it so difficult to wait for God’s timing. God bless you.
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