Galatians 4:22-31

For it is written, that Abraham had two sons, one by the handmaid, and one by the freewoman. Howbeit the son by the handmaid is born after the flesh; but the son by the freewoman is born through promise. Which things contain an allegory: for these women are two covenants; one from mount Sinai, bearing children unto bondage, which is Hagar. Now this Hagar is mount Sinai in Arabia and answereth to the Jerusalem that now is: for she is in bondage with her children. But the Jerusalem that is above is free, which is our mother. For it is written, Rejoice, thou barren that bearest not; Break forth and cry, thou that travailest not: For more are the children of the desolate than of her that hath the husband. Now we, brethren, as Isaac was, are children of promise. But as then he that was born after the flesh persecuted him that was born after the Spirit, so also it is now. Howbeit what saith the scripture? Cast out the handmaid and her son: for the son of the handmaid shall not inherit with the son of the freewoman. Wherefore, brethren, we are not children of a handmaid, but of the freewoman.