King James Bible
"For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman."
Paul appeals to Scripture's authority, referencing Genesis to ground his allegorical argument. This phrase signals he's about to use a well-known Old Testament narrative to illustrate the difference between law and grace. Paul identifies Ishmael and Isaac, though not by name here, as central figures in his theological comparison. Abraham's two sons will represent two different covenants—one of slavery and one of freedom. The contrast between Hagar (the bondmaid/slave) and Sarah (the freewoman) establishes the foundation for Paul's allegory. Their different social statuses—slave versus free—prefigure the spiritual conditions of those under law versus those under grace.