[Avodah] Learning on Shavuos - Two Scenarios

[Marty Bluke]

The Mishna Berura in Siman 527 Sif Katan 3 writes that the minhag was
to make early Shabbos specifically when Yom Tov falls out on Friday.
The reason is as follows.

The Gemara in Pesachim (46a) has a machlokes Rabba and R' Chisda, is
there an issur d'oraysa if you cook on Yom Tov for a weekday. Rabba
says no and R' Chisda says yes. Rabba says no because of ho'eel, since
guests can come and eat the food it falls under the heter of ochel
nefesh. R' Chisda disagrees. Rabba asks R' Chisda according to you how
do we cook on Yom Tov for Shabbos? R' Chisda answers that tzorchei
shabbos naasim, b'ytom tov, that you are allowed to prepare from
Shabbos to Yom Tov.

There is a big nafka mina between the 2 opinions. What happens if you
finish cooking very late in the day right before Shabbos? According to
Rabba you are in trouble, the heter of ho'eel does not apply as there
was not time for guests to come and eat the food on Yom Tov while
according to R' Chisda there is no problem as you are allowed to
prepare from Yom Tov to Shabbos.

It is not clear who we pasken like, Rabba or R' Chisda. Based on this
the Mishna Berura writes that we should be choshesh for Rabba's
opinion and finish cooking early in the day. Therefore the Mishna
Berura writes the minhag was to make early shabbos.

The question is how does the minhag help. There are 2 possibilities:
1. It is a pyschological thing. If you make early shabbos then you
will prepare earlier in the day.
2. It is a din.

There is a a big nafka mina, many people will finish their preparation
2 minutes before candle lighting whenever it is, therefore if early
shabbos is because of 1 you gain nothing as people will finish cooking
2 minutes before lighting candles for early shabbos.

What is pshat that it is a din? The answer may be as follows. When you
make early shabbos, you are turning a day of chol into Shabbos, you
are adding kedusha. However, when that day is also Yom Tov, you cannot
take away the kedushas Yom Tov, you can only add kedusha. Therefore,
that time period of early shabbos has both kedushas. If this is true,
if you finish cooking before early shabbos, then there is still time
for ho'eel to kick in, until Yom Tov is actually over. Any food eaten
before shkia will be a kiyum of simchas Yom Tov as well and therefore
the heter of ochel nefesh would apply as well as the sevara of ho'eel.