Paul's doctrinal argument for justification by faith alone apart from the works of the law is illustrated in these verses by way of an allegorical presentation of Old Testament events. The covenant of the flesh by law is contrasted with the covenant of promise by faith; Paul asks the Galatians, "Are you children of Sarah (promise) or Hagar (flesh)?" Ultimately, flesh leads to bondage and promise to freedom; therefore, we must know who are spiritual mother is.