OPINIONS: The Mishnah describes a case in which a Yevamah was Asur to one of
the brothers of her husband, and then her Isur was removed. The Mishnah
states that since she was Asur to that brother for one moment, she remains
Asur to him forever.
The case of the Mishnah is when two brothers (Reuven and Shimon) are married
to two sisters (Leah and Rachel), and a third brother (Levi) is married to
an unrelated woman. When Reuven dies childless, his wife, Leah, falls to
Levi for Yibum. She may not do Yibum with Shimon, because she is an Ervah to
him ("Achos Ishto," the sister of his wife, Rachel). After Levi does Yibum
with Leah, the wife of Shimon dies. When Levi dies childless, even though
Shimon's wife has died and thus Leah is no longer an Ervah of "Achos Ishto"
to Shimon, she nevertheless remains Asur to him because at the time that she
first fell to Yibum she was an Ervah to him, and thus she remains an "Eshes
Ach she'Lo b'Mekom Mitzvah."
Rav Yehudah in the name of Rav says that the same applies during the first
Nefilah to Yibum. If, at the time that the woman fell to Yibum for the first
time, the Yavam is married to her sister, then even if the sister dies
afterwards the woman is exempt completely from Yibum.
The Gemara says that we might have thought that there is a difference, in
this latter casee, between when there are other brothers who can do Yibum
with the Yevamah and when there are no other brothers except the one to whom
the Yevamah is an Ervah. When there are other brothers, we might have
thought that she can fall to Yibum to Shimon if her sister, Shimon's wife,
dies.
Why does the presence of other brothers give more reason to believe that the
Yevamah can do Yibum with her sister's husband after her sister dies?
(a) From RASHI it appears that the logic is that since there is an existing
Zikah (due to the presence of the other brother to whom this woman is
Zekukah), when the brother to whom she was heretofore Asur becomes eligible
to do Yibum with her the Zikah can extend to that brother as well. In
contrast, when there was no other brother to whom Zikah applied at the time
of the death of her husband, Zikah cannot be created when her Isur to the
surviving brother is removed.
(b) There is another way to understand the Gemara based on the words of
TOSFOS (2a, DH v'Achos Ishto). According to Tosfos, Zikah can start either
at the moment that the husband dies, or at any other time after he dies. The
reason the Mishnah asserts that his wife remains Asur to the brothers
forever when she was Asur at the moment that she fell to Yibum is not
because the Zikah cannot be effected after the moment of her husband's
death. Rather, the reason is because "Deracheha Darchei Noam" -- the ways of
the Torah are ways of pleasantness, and it would not be pleasant for a woman
who has been exempt from Yibum (and has been permitted to marry someone
else) to suddenly be obligated to do Yibum (and have to separate from her
husband if she has remarried) at a later time. For this reason, if a Yevamah
was Asur to the Yavam at the time of her husband's death, she remains Asur
to the him under all eventualities, and is permitted to marry others. (The
Gemara mentions the logic of "Darchei Noam" on Daf 87b, regarding a case
where a man died leaving behind a child, and then the child died. Since, at
the time of the man's death, there was no obligation to do Yibum (because he
left behind a living child), his wife cannot be obligated to do Yibum later
when the child dies. Once she was already permitted to marry someone else,
she always remains permitted.)
The Gemara now is very clear. If the reason why she does not fall to Yibum
when the Isur Ervah to Shimon is removed is because of "Deracheha Darchei
Noam," then we might have thought that such reasoning applies only in a case
where she was exempt from Yibum entirely (such as when there was only one
remaining brother, and she was Asur to that brother with an Isur Ervah) and
she was able to marry others. But in a case where she was not exempt from
Yibum because there was another brother to whom she was not an Ervah, there
is nothing unpleasant involved with allowing a second brother to also
perform Yibum, even if she was Asur to that brother when she first fell to
Yibum. This does not involve a lack of "Darchei Noam" since, anyway, she
could not yet remarry because she was required to do Yibum or Chalitzah with
the other brother.
Rav taught that even in such a case, requiring her to do Yibum with the
brother to whom she was originally Asur is nonetheless considered a lack of
"Darchei Noam." It is indeed unpleasant for a woman to be subject to do
Yibum with a brother with whom she thought she no longer had any ties. (When
we say that she is Asur in such a case because of "Darchei Noam," that does
not mean that she is not prohibited with an Isur of "Eshes Ach" to that
brother. Rather, it means that it is logical that the Torah would not
require her to fall to Yibum in such a case and thus the Isur of "Eshes Ach"
remains and the Zikah does not take effect.)
(According to Tosfos' explanation, a Yevamah remains Asur forever during the
*first* Nefilah and after the *second* Nefilah for two different reasons.
During the first Nefilah, the logic prohibiting her is "Darchei Noam" -- she
cannot be subject to the person from whom she was previously exempted from
Yibum. This logic, though, cannot prohibit her to that Yavam when she falls
to him from a second Nefilah, since there is an entirely new *cause* for her
to fall to him. Rather, during the second Nefilah she is prohibited because
she is an Eshes Ach she'Lo b'Mekom Mitzvah (to the Yavam) from the first
Nefilah, and she can never again become permitted to the Yavam. This
presents somewhat of a problem, since the Gemara later (32a) seems to
consider the two Isurim related. The Gemara there tells us that once we are
told that a Yevamah who was once Asur remains Asur after the second Nefilah,
it is obvious that if she was once Asur, she should be Asur during the first
Nefilah -- M. Kornfeld)