Why does the Torah use the double expression "Besulah, v'Ish Lo Yeda'ah"?
Rashi (citing the Midrash Rabah): The Cana'ani women 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 nobody knew 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 the Riva holds like the opinion that she was 14 - Refer to 25:20:1:1***). Refer also to 24:16:1.1:1.
QUESTIONS ON RASHI
Rashi writes: "A virgin - in the place of Besulim." Why does the Torah need to testify to this; she was younger than three years old (Rashi to 25:20) at the time (and therefore certain of being physically a Besulah)?
Gur Aryeh: Avraham waited three years before sending Eliezer. Avraham counted from when he heard the news of Rivkah's birth, not from her birthdate, so she was actually older than three at this time. Rashi means that she was not yet in her fourth year.
Rashi writes: "No man knew her - [even] unnaturally." If so, why must the verse say the first phrase, "a virgin"?
Gur Aryeh: She was not a Mukas Etz (i.e. the Besulim were fully intact).