The Gemara gives two answers. First, the Gemara says that the money in doubt
does not go to Shekalim in this case, because it is not certain that it will
be used for Korbanos at all -- it might be left over and go to Sheyarei
ha'Lishkah and be used for fixing the city's walls. Second, the Gemara says
that if the money is between the two boxes, it is considered like the money
of "one who died" ("k'Mi sh'Mes"), and therefore the money goes to Nedavah.
What does the second answer mean? What does being like the money of one who
died have anything to do with the questionable money at hand?
(a) The text of the Gemara of RABEINU MESHULAM reads "k'Mi
*she'Mishtayerah*" -- the money that is found between the boxes is
considered *as if it was left over*. The Halachah is that when there are
Korbenos Temidin which were purchased but were not used, they are brought as
Olos for Kayitz ha'Mizbe'ach (11b). The money that is in doubt is treated
like *leftover* Temidin (since it will be leftover out of doubt) and is used
for Kayitz ha'Mizbe'ach.
(b) The text of the Gemara of the TALMID SHEL RABEINU SHMUEL BAR SHNEUR
reads "k'Mi *she'Mis'ameh*" -- the money is treated as if it was money of
Shekalim that became totally *mixed together* with the money of Nedavah
("Mis'ameh" comes from the word "Te'um," or twin, implying that it was mixed
in with the money which is all used for the *same* thing (Olos), i.e.
Nedavah). Still, though, why should the money be used for Nedavah? If
Shekalim is more Chamur, it should go to Shekalim!
The Talmid Shel Rabeinu Shmuel bar Shneur learns that the Gemara never
actually thought that Nedavah is less Chamur. It knew all along that Nedavah
is *more* Chamur than Shekalim (because the Korbanos of Nedavah are
completely consumed by the Mizbe'ach). The Gemara is just asking whether
there is *another* reason why the money should go to Nedavah, other than the
reason that Nedavah is more Chamur. The Gemara answers in its second answer
that there is no other reason, and the reason the money goes to Nedavah is
because it is more Chamur. It is like a mixture of two types of money, in
which case all of the money is treated like the more Chamur type, which is
Nedavah in this case.
This explanation is consistent with the RAMBAM's explanation (in Perush
ha'Mishnayos). The Rambam writes that Nedavah is certainly more Chamur than
Shekalim, because the money of Nedavah is all brought as Olos, which are
totally burned, whereas some of the money of Shekalim is used for Shelamim
which are not totally burned. In fact, the Rambam might have had the same
Girsa as the Talmid Shel Rabeinu Shmuel bar Shneur, and perhaps he based his
explanation on that Girsa. "K'Mi sh'Mis'ameh" could mean that the money is
used for the type that is all equal -- that is, the type of donation which
is all used for one type of Korban, Olos, and that is Nedavah (as opposed to
Shekalim, some of which are brought as Chata'os Tzibur). The Gemara,
therefore, concludes that Nedavah is more Chamur.
(c) RABEINU SHLOMO SIRILIYO has the Girsa that we have ("k'Mi sh'Mes") and
says that the money in doubt here is used for Nedavah just as it is used for
Nedavah in the case of a person who contributed money for the Shekalim and
then died. In that case, the money is considered ownerless and is not placed
together with the rest of the Shekalim, because if we were to place it there
on behalf of the deceased, it would be coming from us and not from the
original contributor. Here, too, the money resting outside of the box of
Shekalim cannot be placed back into the box, because it will not be the
original owner placing it there, and therefore it is as if it has no owner.
According to this explanation, the Gemara is assuming that the money
between the boxes was not placed into one of the boxes and fell out, but
rather it fell onto the floor *before* it was placed in a box. That is why
it is considered like the money of one who died; it is was not given as a
Shekel by its owner money cannot be given to Shekalim without being given
expressly by its owner. (See the commentary of Har Efraim there.)
(d) RAV CHAIM KANIEVSKY suggests an original explanation for our Girsa. He
explains why it is that when a person dies before his Shekel is placed in
the Lishkah, the money is not placed with the other Shekalim but is used for
a public Nedavah (Kayitz ha'Mizbe'ach). The reason is that the Shekel must
be given by someone who is obligated to give it, and a dead person is not
obligated. Therefore, even if the money of Shekalim is more Chamur than the
money of Nedavah, the money found between the boxes does not go to Shekalim,
because if it actually fell from the Nedavah box, then giving it to the
Shekalim would be giving it as a voluntary donation, and we are *not
allowed* to give a voluntary donation to the Shekalim. Therefore, the money
goes to Nedavah.