But God told Abraham, “Do not be upset over the boy and your servant. Do whatever Sarah tells you, for Isaac is the son through whom your descendants will be counted.
Isaac pleaded with the Lord on behalf of his wife, because she was unable to have children. The Lord answered Isaac’s prayer, and Rebekah became pregnant with twins.
What’s more, your relative Elizabeth has become pregnant in her old age! People used to say she was barren, but she has conceived a son and is now in her sixth month.
These two women serve as an illustration of God’s two covenants. The first woman, Hagar, represents Mount Sinai where people received the law that enslaved them.