An Aseh is not punishable with Malkus. What, then, is the verse adding to
the Halachah l'Moshe mi'Sinai? Without the Aseh, it would still be obvious
that offering the Vlad Chatas as a Korban would be Asur, because of the
Halachah l'Moshe mi'Sinai! (Rebbi Akiva indeed does not learn from a verse
that there is an Isur Aseh involved. The SHITAH MEKUBETZES explains that
Rebbi Akiva holds that if it is a Halachah l'Moshe mi'Sinai then it is not
necessary to have also an Isur Aseh.)
(a) REBBI MEIR ARIK in TAL TORAH cites the MORDECHAI who says that a
Halachah l'Moshe mi'Sinai normally teaches a law that is only l'Chatchilah.
If one ignores or transgresses the Halachah l'Moshe mi'Sinai, then what he
does is still acceptable b'Di'eved. According to this, our Gemara is easily
understood. Without the verse and with only the Halachah l'Moshe mi'Sinai,
we would have thought that if one offers the Vlad Chatas as a Korban, the
offering is valid b'Di'eved. The verse teaches that even b'Di'eved, the Vlad
Chatas is not acceptable if offered as a Korban.
(b) The RAMBAM (Hilchos Shechitah 5:2, Perush ha'Mishnayos 6:7) implies that
a Halachah l'Moshe mi'Sinai differs from a Halachah that is written
explicitly in the Torah in that we are lenient in the case of Safek.
The RAMBAN (Sefer ha'Mitzvos, Shoresh 1) challenges the Rambam. If a
Halachah l'Moshe mi'Sinai is mid'Oraisa like any Mitzvah explicitly written
in the Torah, how, then, can we treat its Safek like a Safek d'Rabanan and
The Rambam seems to be following his own reasoning elsewhere (Hilchos
Kil'ayim 10:27, Avos ha'Tum'ah 16:1, Bi'os Asuros 18:17), where he holds
that a Safek d'Oraisa is *l'Hakel*, mid'Oraisa, and it is only l'Hachmir
mid'Rabanan (that is, the Rabanan decreed that a Safek d'Oraisa should be
l'Hachmir). The Rabanan, therefore, may be lenient with a Safek involving a
Halachah l'Moshe mi'Sinai, even though a Halachah l'Moshe mi'Sinai has the
same status as a Halachah written in the Torah. (C.f. Insights to Shabbos
55:1:c for an example of a Halachah d'Oraisa that is not written explicitly
in the Torah being treated differently than a Halachah d'Oraisa that is
written explicitly in the Torah.)
According to this, our Gemara is saying that had we only had for the
Halachah l'Moshe mi'Sinai, we would have been lenient in a case of a Safek.
Now that we see that it is an Aseh as well, we are Machmir even in the case
of a Safek.