(a) The RAN writes that since mid'Oraisa she is believed, it must be that
the principle of "Afka'inu Rabanan Kidushei Minei" is working here; the
Chachamim retroactively annulled the original Kidushin between the man and
woman and, consequently, she was not married at the time of the Z'nus.
According to this opinion, we still believe the woman's testiony, but she
does not become Asur to her husband as a result, since "Afka'inhu" makes it
that she was not married to him at the time of the Z'nus.
However, this Heter applies only to the Isur of Eshes Ish; if she was
married to a Kohen and, for example, she sinned with a Nochri, then she will
be Asur to her husband, because annulling the Kidushin retroactively will
*not* rectify the fact that she lived with a Nochri and thereby became
disqualified from marrying a Kohen (any Kohen). The same, of course, will be
true if the Isur preceded the marriage.
(b) The RAN cites another opinion, which is the opinion of the RASHBA and
TOSFOS, who say that although the woman is believed, we allow her to remain
married to her husband because of the principle, "Yesh Ko'ach b'Yad
Chachamim la'Akor Davar Min ha'Torah" -- the Chachamim are empowered to
override a Halachah of the Torah where they see it necessary to do so.
The Ran asks that this principle applies only when the Halachah will be
trangressed passively ("Shev v'Al Ta'aseh") and not in situations such as
this one where, by continuing to live with his wife, the husband is
*actively* transgressing the Halachah ("Kum v'Aseh"). The other Rishonim
counter that in cases of great necessity the Chachamim are empowered even to
override a Halachah of the Torah with "Kum v'Aseh."
(c) The RAN cites another opinion that says that in actuality, the woman's
testimony was *never* accepted; since she is obligated ("Meshu'abedes") to
her husband, she is not believed to prohibit herself upon him and thereby
nullify her obligation. However, the Mishnah Rishonah maintained that she
was believed, because it is unlikely that she would lie about such an
embarrassing matter and thus she is presumably telling the truth. However,
when it became known that women were willing to suffer the embarrassment in
order to obtain a divorce, the Chachamim repealed their original Takanah to
We see, then, that there is a Machlokes Rishonim regarding the original
Halachah of the Mishnah Rishonah, which maintained that the woman is
believed. According to one opinion, the woman was believed mid'Oraisa, and
according to another opinion, the woman was believed due to a Takanah
d'Rabanan. According to the opinion that she was believed mid'Oraisa,
although the general rule is that "Ein Davar she'b'Ervah Pachos mi'Shenayim"
(a matter of prohibitted relationship requires at least two witnesses) and
thus we should require two witnesses in order to prohibit a woman to her
husband, we base our acceptance of her testimony on the principle of
"Shavyah Anafshei Chatichah d'Isura," which states that one is believed on
questions of Isur insofar as it relates to oneself. Therefore, the woman is
not allowed to be with her husband, although, in actuality, the husband has
no reason to believe her. The reason we force the husband to divorce her is
in order not to force *her* to transgress an Isur.
The RASHBA writes that although we do not believe the woman, if the
*husband* says that he believes her, then he must divorce her, for in such a
case he has invoked the principle of "Shavyah Anafshei Chatichah d'Isura"
upon himself. The REMA (EH 178:9), though, writes that the rationale of the
Mishnah Acharonah *not* to believe the woman -- that we fear that perhaps
she has set her eyes on another man and therefore wants a divorce -- applies
even to the husband, whom we suspect of similar intent. Therefore, nowadays
(in contrast to the times before the Cherem of Rabeinu Gershom prohibiting
bigamy), even if the man says that he believes the woman, we suspect that he
has impure intent and thus we allow them to continue living together. The
YAM SHEL SHLOMO disputes this ruling on the grounds that since the woman
originated the statement concerning her adultery, there is no reason to
suspect the husband of impure intent.