However, that verse appears in the Parshah (Acharei Mos) that discusses the
Isur Lo Ta'aseh of having relations with the various Arayos; it does not
openly prescribe the punishment of Kares for Eshes Achiv in that Parshah. It
might therefore be possible to argue that the verse "Ervas Achicha Hi" only
includes "Eshes Achiv Min ha'Em" in the Lo Ta'aseh, but not in the punishment
of Kares. TOSFOS (2a, DH Eshes Achiv), though, points out that the Mishnah at
the beginning of Yevamos lists "Eshes Achiv Min ha'Em" as one of the Arayos
that exempt a person from Yibum, and the Gemara (3b) says that all of the
Arayos that exempt a person from Yibum are Arayos which are punishable with
Kares. We see, then, that the Mishnah takes it for granted that "Eshes Achiv
Min ha'Em" is Chayav Kares.
Tosfos, however, points out that there are other sources that imply that
there is *no* Kares for "Eshes Achiv Min ha'Em." The TORAS KOHANIM (Kedoshim
11) and YERUSHALMI (Shabbos 7:2) explain that the verse discussing the Kares
of Eshes Achiv (in Parshas Kedoshim) adds the words "Nidah Hi," in order to
teach that the Isur of "Eshes Achiv" is punishable by Kares when it is
similar to a Nidah; just like the Isur of Nidah has a Heter (she can become
Tahor), so, too, the type of "Eshes Achiv" that is Chayav Kares is that which
has a Heter, i.e. "Eshes Achiv Min ha'Av" (the Heter being a situation of
Yibum). This implies that only "Eshes Achiv Min ha'Av" is included in the
punishment of Kares and not "Eshes Achiv Min ha'Em."
Although the Toras Kohanim and Yerushalmi might disagree with our Gemara's
interpretation of "Nidah Hi," they certainly could not be arguing with the
Mishnah at the beginning of Yevamos, which states that "Eshes Achiv Min
ha'Em" is exempt from Yibum (because it carries a punishment of Kares). How
did the Toras Kohanim and the Yerushalmi learn the Mishnah?
(a) TOSFOS (2a) and the RAMBAN (54b) suggest that perhaps the Toras Kohanim
means to say the same thing as our Gemara says (on 54b). The Gemara there
derives that "Eshes Achiv Min ha'Av" -- in a case where the brother was
childless, but *divorced* his wife -- is punishable with Kares, despite the
fact that it is *permitted* to marry such a woman in a situation of Yibum,
i.e. if her husband dies childless. This is learned from the words "Nidah
Hi," which imply that the verse applies to the type of "Eshes Achiv" that can
have a Heter (i.e., she is like a Nidah, who can become permitted). The Torah
is telling us that even "Eshes Achiv Min ha'Av" will sometimes incur a
punishment of Kares.
Perhaps that is what the Toras Kohanim means as well: it is not saying that
the verse is referring *only* to "Eshes Achiv Min ha'Av," but that the verse
is referring *even* to "Eshes Achiv Min ha'Av." "Nidah Hi" teaches that even
though that Eshes Ach has a Heter (when the brother dies and his wife falls
to Yibum), the Chiyuv Kares remains when the brother divorces his wife.
(b) Tosfos (2a and Kerisus 14b), however, rejects this explanation based on
the wording of the Yerushalmi and the Toras Kohanim. Instead, he suggests a
different explanation. The Toras Kohanim and Yerushalmi do not mean to exempt
"Eshes Achiv Min ha'Em" from Kares. Rather, they learn from the words "Nidah
Hi" that "Eshes Achiv Min ha'Em" is not punished with *Ariri*, whereas all of
the other Arayos are punished with Ariri. (Even though the verse mentions
Ariri only with regard to "Dodaso" (one's aunt) and "Eshes Achiv," by
applying the Hekesh of Rebbi Yonah, which compares all of the Arayos to each
other, we can learn from "Dodaso" that all of the Arayos carry the punishment
of Ariri.)
(Perhaps the logical understanding of this distinction is that since the
person might have pure intentions when he has relations with the wife of his
brother (from his mother) -- since he intends to "build the family" of his
deceased brother by bearing children with his wife, such as is the case with
Yibum of a paternal brother's wife -- Midah k'Neged Midah the Torah does not
punish him with the death of his children - M. Kornfeld.)
Tosfos points out that this explanation is viable only if Ariri and Kares are
two separate punishments. Kares means simply "early death," while Ariri adds
the aspect of dying childless. This is not the view of RASHI here (DH
Aririm).
If Kares and Ariri are different punishments, though, what is the Gemara's
intention here when it asks why the Torah says "Aririm Yiheyu" in the verse
of the Isur of "Dodaso?" The Torah has to write "Aririm" to teach the
additional punishment of Ariri! The answer to this question is that the
Gemara is asking why it says "Aririm" *twice*, once in the verse of "Dodaso"
and a second time in the verse of "Eshes Achiv." The Torah could have
mentioned it only once, and we would have learned from there that all the
other Arayos are also punished with Ariri, through the Hekesh of Rebbi Yonah.
(c) A third possibility, which is not mentioned by the Rishonim, is that the
Yerushalmi actually exempts "Eshes Achiv Min ha'Em" from Kares. The
Yerushalmi maintains that even though there is no Kares for "Eshes Achiv Min
ha'Em," that relationship still exempts a person from Yibum, because it is
included in the Hekesh of Rebbi Yonah, which teaches which women are exempt
from Yibum (as Tosfos (3b DH Mah Achos) explains. That Hekesh is written in
Parshas Acharei Mos, in which Eshes Achiv me'Imo *is* included (through the
words "Eshes Achicha Hi"), as our Gemara concludes. (Even though the verse
which Rebbi Yonah uses for the Hekesh to compare all of the Arayos (54b) with
each other specifically mentions Kares, Eshes Achiv me'Imo is exempt from
Kares because, according to the Yerushalmi, another verse ("Nidah Hi")
excludes "Eshes Achiv Min ha'Em" from Kares.)
Acharonim adduce proof from another statement in the Yerushalmi that the
Yerushalmi indeed maintains that "Eshes Achiv Min ha'Em" is not punished with
Kares. The Mishnah in Kesuvos (29a) lists types of Na'aros for which a man
will be obligated to pay a penalty if he rapes them. One of the Na'aros
mentioned in the Mishnah is "Eshes Achiv... even though she is Asur with an
Isur Kares." The YERUSHALMI (cited by TOSFOS there, DH v'Al Eshes Achiv) asks
how there can be a penalty for raping "Eshes Achiv?" In order for there to be
a penalty, the Na'arah must be a Besulah, and must not be married at the time
(because if she is, the rapist is given the death penalty and not a monetary
penalty). If the rapist's brother dies and his wife is still a Besulah, the
dead brother obviously did not bear children from her. If so, the live
brother is not prohibited to her at all -- to the contrary, he has a Chiyuv
to do Yibum with her, and thus there should be no Kares nor a penalty! The
Yerushalmi answers that the Mishnah is referring to a case where the brother
who died had children from another wife, and thus his wife does not fall to
Yibum.
Why does the Yerushalmi not give a very simple answer? The Mishnah could
simply be referring to an "Eshes Achiv *Min ha'Em*!" Even though her husband
died childless, there is no Chiyuv of Yibum with her (since the brothers do
not share the same father), and thus the brother is Chayav to pay a penalty
for raping her! (TOSFOS CHADASHIM on the Mishnayos; this is indeed how the
RIF in Kesuvos answers the Yerushalmi's question. See also RASHASH, there.)
If the Yerushalmi maintains that "Eshes Achiv Min ha'Em" bears no punishment
of Kares, then the Yerushalmi's question is easy to understand. The Mishnah
cannot be discussing "Eshes Achiv Min ha'Em" because it clearly says that the
Eshes Achiv of the Mishnah incurs the punishment of Kares!
(The RIF, and others, also suggest that the Eshes Achiv of the Mishnah might
be his brother's *divorced* wife, and not his widow. It is possible, however,
that the Yerushalmi understood that this cannot be so, for only later does
the Mishnah (Kesuvos 38a) introduce the Halachos of raping a divorcee. (In
fact, one Tana there says that in the case of a divorcee, there is no
monetary penalty at all). Although all the commentaries (see Rashi there)
equate the laws of a divorcee to those of a widow, it is possible that the
Yerushalmi learned otherwise. The Yerushalmi might have maintained that all
Tana'im agree that there *is* a monetary penalty for a widow, because she
returns to her father's house after becoming widowed -- see the Mishnayos in
Nedarim 70a, 71a.)