1. TOSFOS (DH Hacha Nami) explains that the Get of an Arusah specifies in it
that the wife is only an Arusah. If the woman receives the Get only after
she is married (with Nesu'in), then people know that the time written in the
Get must not be the date on which it was given, since it is common knowledge
that she was divorced from Nesu'in, and not during Erusin. Therefore, if the
wife tries to collect Peros -- on the basis of the early date written in the
Get -- from those who bought them from the husband, the buyers will probably
be informed that the date cannot be correct. They will therefore easily foil
her intentions and bring testimony that she was married with Nesu'in before
the Get was given.
However, with regard to the legitimacy of the child, we do not take chances.
People do not have a personal interest in legitimizing the child, and
perhaps they will not be aware of the "common knowledge" that the woman was
once married, and that the date written in the Get is not the date on which
the Get was given.
Tosfos asks, however, that if this is correct, then a Get Mukdam of an
Arusah effectively contains no proof of the date on which it was actually
given. Consequently, Reish Lakish should invalidate it because the *husband*
might unlawfully sell the Peros even after the signing of the Get (at which
time, by law, he loses the rights to the Peros; see Gemara 17b), and the
wife will not be able to prove that he is a thief, since the date of the
Chasimah is not written in the Get. Tosfos leaves this question unanswered.
The TOSFOS HA'ROSH answers that in this case, the husband does not lose
Peros even according to Reish Lakish until the time that he *gives* the Get
(and not form the time the Get is signed). Since the Get was delivered after
the date written in the Get, the witnesses (Edei Mesirah) will spread the
word that the date is not reliable, and the woman will not be able to
unlawfully collect Peros from the buyers based on the date written in the
Get. (See Tosfos 17b, DH Ad, regarding the opinion of Rebbi Yochanan.)
The Rosh does not explain clearly why the husband retains the Peros until
the giving (Nesinah) of the Get in this case, in contrast to a normal Get.
The TAZ (EH 132:1) suggests that the reason the man normally loses Peros
from the time of the Chasimah according to Reish Lakish is because the
husband has made a decision to divorce her (see end of 18a, according to
Rebbi Shimon), and from that point on he loses his rights to the Peros. In
this case, since the husband married her after writing the Get, he obviously
did not decide to divorce her at the time of the writing, and therefore he
does not lose the Peros until he actually utilizes the Get.
Alternatively, perhaps the Rosh has a different intention. The Rosh means
that the husband loses the Peros from the time of the Nesinah because the
day of the Nesinah of this Get probably was the very same day as the day of
its Chasimah. We may assume that the husband had the Get signed on the same
day that it was delivered since "a person does not hasten his grief" ("Lo
Makdim Inish Puranusa l'Nafshei") by having a Get signed before he plans on
giving it (Gitin 18a). Therefore, the wife could bring the Get to Beis Din
as soon as she receives it in order to prove what day the Chasimah and
Nesinah took place, which was the point in time at which the husband lost
his rights to the Peros (as Tosfos writes on 17b DH Ad She'as).
The obvious question on this logic is, why, then, does Reish Lakish require
the date to be written in *any* Get? We should always assume that the Get
was signed at the same time that the Get was delivered, and the date of the
Get's delivery can be confirmed even without writing a date in the Get
(since she can bring the Get to Beis Din on the day of its delivery to prove
that all future Peros are hers)!
The Rosh might hold that Reish Lakish requires the date to be written in the
Get because there are times at which a husband sends a Get to his wife with
a Shali'ach and it takes time for the Get to arrive in the woman's hands
even though the husband *sent* it on the day it was signed. Therefore, in
order to prove on what day the Get was signed, the husband must write in the
Get the date on which it was signed. Because of this, the Rabanan required
the date to be written in all Gitin.
However, in the case of our Gemara, the husband who wrote a Get for his wife
while she was an Arusah was obviously together with his wife at the time
that he had the Get written. If he wanted to divorce her after the Nesu'in,
he would not have to send the Get with a Shali'ach; he would simply have the
Get, which was already written, signed by two witnesses and he would then
deliver it in person.
(Tosfos might not have accepted this approach because he maintains that
Reish Lakish argues with Rebbi Yochanan and holds that we *do* suspect that
a person will keep a Get after the Chasimah and not deliver it until later.
Therefore we cannot assume that the day of this Get's Nesinah was also the
day on which it was written.)
2. The RASHBA answers that we are not concerned that the husband will give
this Get to his wife after the Nesu'in (and after he sells Peros), because
no witnesses would agree to sign a Get for a Nesu'ah that says in it that
the wife is an Arusah. (Even if a witness might not notice that the date is
early, he will certainly notice that the Get says that she is an Arusah when
she really is a Nesu'ah.)
The Rashba does not explain why, according to this, the Gemara does not
permit writing an early date in an Arusah's Get because of the problem of
the date in the Get preceding the conception of her child ("Gitah Kodem
li'Vnah"). If the Get will not be signed after the Nesu'in (but only during
Erusin), then she certainly should not be pregnant! The Acharonim (HE'OROS
B'MASECHES GITIN and others) explain that the Rashba means that the
Chachamim take more precautions to prevent rumors about the legitimacy of
the child than they take to protect the people who purchase the Peros.
Therefore, only with regard to preventing rumors about the legitimacy of her
child are we concerned that witnesses signed the Get even after the Nesu'in.
(See below.)
3. The RAMBAN explains, like the Rashba, that witnesses certainly will not
agree to sign a Get for a Nesu'ah which says in it that the woman is an
Arusah. However, we *are* concerned that witnesses might sign the Get on the
*day* of the Nesu'in, since they will think that doing so will not cause
anyone to lose the Peros, since, even if it the Get has an earlier date in
it, it will not prevent the husband from selling the Peros later on the same
day (after the divorce), since he could claim that he sold the Peros before
the Get was given without being contradicted by the date written therein.
However, there *will* be a concern that the Get precedes the conception of
the child, since he might have had relations with her, and the date written
in the Get will be during Erusin -- long before the beginning of the
pregnancy.
The Ramban adds that even if witnesses will not agree to sign the Get of an
Arusah after the Nesu'in, they might sign it on the *day* of the Nesu'in but
*before* the Nesu'in takes place (the date written in the Get, however, is a
much earlier date). The husband might then present it to her later that day,
after he has married her with Nesu'in and had relations with her. This seems
to be the intention of RABEINU KRESKAS as well, and this might also be the
intention of the Rashba (above, #2, unlike the interpretation of the
Acharonim cited above).