What does 'cast out the bondwoman and her son' mean in Galatians 4:30?
According to the context, it means Hagar and Ishmael—representing the law, legalism, and the flesh—must be cast out. The son of the bondwoman cannot be heir with the son of the free woman. Ishmael and Isaac could have no interrelationship: Ishmael stood for law, while Isaac stood for grace and freedom.
Les explains that Galatians was written to the churches of Galatia because Judaizers were trying to put Gentile believers under law, but they were under grace. In chapter 4 Paul uses Isaac and Ishmael as an analogy. Ishmael was of the flesh, earthly, not the spiritual seed or promises as Isaac was. Verse 30’s “cast out the bondwoman and her son” refers to Hagar and Ishmael, who stood for the law and the flesh. The son of the bondwoman shall not be heir with the son of the free woman. Ishmael and Isaac could have no consort or interrelationship, because Ishmael stood for the law and legalism, while Isaac stood for grace and freedom.
Nevertheless what saith the scripture? Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman.