Why the double expression "Besulah v'Ish Lo Yeda'ah"?
Rashi citing the Midrash Rabah: The Kena'aniyos it appears, would guard their virginity, but were not particular about unnatural sex. Rivkah was particular about both. 1
Malbim: She never went out before, so men did not know (recognize) her.
Riva: This is difficult according to Rashi's opinion that Rivkah was less than three at the time. Even if she had Bi'ah, her Besulim would return! (Riva understands Rashi (25:20) to mean that Yitzchak waited until she was exactly three to marry her. Perhaps Riva holds like the opinion that she was 14