דברים כב:כג מדרש: Sifrei Devarim

(Devarim 22:23) "If there be a na'arah, a virgin, betrothed": We are hereby taught that he is not liable (to stoning) unless she be a na'arah (and not a bogereth [viz. #238]), a virgin, and betrothed to a man (and not married).