Galatians 4:22-25

22For it is written that Abraham had two sons, one by a slave and the other by a free woman.

23But the one by the slave was born as a result of the flesh, while the one by the free woman was born through promise.

24These things are being taken figuratively, for the women represent two covenants. One is from Mount Sinai and bears children into slavery — this is Hagar.

25Now Hagar represents Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children.