King James Bible
"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."
Paul appeals to Genesis 21:10, where Sarah demands Hagar and Ishmael's expulsion, using Scripture as his ultimate authority. This rhetorical question introduces a harsh but divinely sanctioned solution to the conflict between law and grace. The command refers to expelling Hagar (representing the old covenant of law) and Ishmael (those born into slavery under the law). Paul applies this allegorically to argue that legalistic Judaism must be decisively rejected from the Christian community. The inheritance belongs exclusively to Isaac (representing believers freed by grace), not to Ishmael (those enslaved to law). This establishes that salvation by works and salvation by faith are mutually exclusive—one cannot possess the promises of God through both systems simultaneously.