Daf Yomi Beitza 15b: Eruv Tavshilin -- The *Biblical* Rabbinic Edict

I posted on this pet theory of mine on the previous daf, but here we have another instance. I suggest that on occasion a pasuk can be darshened by Chazal to grant them a mandate and cause to institute a gezeira or takana. The example from last time was that although the phrasing of the pasuk was such that shaatnez should not be placed upon an individual, but the shaatnez could still be under him, I claim that Chazal made a further derasha based on the fact the the shaatnez was the subject rather than the object. Thus, lo yaaleh alecha was a command to make sure that the shaatnez could not somehow come upon you of its own accord. The was to accomplish that was to make a gezeira that even sitting on shaatnez was forbidden. To reinforce my point, I noted that a phrase in one girsa of the gemara existed, though was emended out, which stated that the reason for the action of the Holy Congregation of Yerushalayim not to sleep even on shaatnez under many layers of bedding was based on a derasha on the verse lo yaaleh alecha.

I now turn to the institution of eruv tavshilin. One midrash states that Avraham kept eruv tavshilin, as an example of even the Rabbinic commandments he kept. Though there is good reason to think, based on the pasuk it is a midrash on -- (if I recall correctly, Bereishit 14:23 -- אִם-מִחוּט וְעַד שְׂרוֹךְ-נַעַל) that the midrash originally said erevei techumin just as it states in terms of Yaakov keeping every jot and tittle of the mitzvot, and was contracted to ע"ת and wrongly
expanded to eruv tavshilin).

The gemara on Beitza 15b reads a pasuk in Nechemia under the assumption that they kept eruv tavshilin. This is in reference to Rosh haShana, Ezra the Scribe reads the Torah before everyone and they weep, and he tells them not to weep, but to make it a day of happiness. The pashut peshat is that they were grieved about not having kept the Torah until then, and he is telling them to be happy. But it is interpreted differently by Rav Chisda:

{Beitza 15b}

ושלחו מנות לאין נכון לו מאי לאין נכון לו
א"ר חסדא שלחו מנות למי שלא היה לו להניח עירובי תבשילין
אבל היה לו להניח ולא הניח פושע הוא

{Nechemia 8:10}:

י וַיֹּאמֶר לָהֶם לְכוּ אִכְלוּ מַשְׁמַנִּים וּשְׁתוּ מַמְתַקִּים, וְשִׁלְחוּ מָנוֹת לְאֵין נָכוֹן לוֹ--כִּי-קָדוֹשׁ הַיּוֹם, לַאֲדֹנֵינוּ; וְאַל-תֵּעָצֵבוּ, כִּי-חֶדְוַת ה הִיא מָעֻזְּכֶם.

10 Then he said unto them: 'Go your way, eat the fat, and drink the sweet, and send portions unto him for whom nothing is prepared; for this day is holy unto our Lord; neither be ye grieved; for the joy of the LORD is your strength.'

What does it mean "unto him for whom nothing is prepared?"
Rav Chisda said: Send portions to he who did not have the ability to set up an eruv tavshilin. But he who had opportunity to set it up and did not is simply negligent.

Thus, Nechemia is commanding them commands relevant to the institution of eruv tavshilin being in place.

Midrash is often what we might consider anachronistic. Thus, Avraham knows of King David's existence, and of various commandments, and can keep them. Similarly, this midrashic interpretation of the verse in Nechemia might be just midrash to derive a homiletic or halachic point, or it can assume fore-knowledge of eventual Rabbinic institution, or it can assume the eruv tavshilin is Biblical, or it can assume that the institution is Rabbinic but was instituted by Ezra or earlier.

Why did Chazal {of whatever age} institute it? We see this, also on Beitza 15b:

מנא הני מילי
אמר שמואל דאמר קרא זכור את יום השבת לקדשו זכרהו מאחר שבא להשכיחו
מ"ט אמר רבא כדי שיברור מנה יפה לשבת ומנה יפה ליו"ט
רב אשי אמר כדי שיאמרו אין אופין מיו"ט לשבת ק"ו מיו"ט לחול

From where do we know this {that one may not cook initially for Shabbat on Yom Tov unless one utilizes the eruv tavshilin?
Shmuel said: Because the Scriptures stated {Shemot 20:7}:

ז זָכוֹר אֶת-יוֹם הַשַּׁבָּת, לְקַדְּשׁוֹ.

7 Remember the sabbath day, to keep it holy.

Remember it from another day {Yom Tov} that comes to cause it to be forgotten.
{This is an asmachta since this is a Rabbinic institution.}

What is the reason?
Rava said: So that he sets aside a nice portion for Shabbat and a nice portion for Yom Tov.
Rav Ashi said: So that they {the people} will say: One may not bake from Yom Tov for Shabbat. All the more so {then} from Yom Tov to a weekday!

From the fact that there is a verse cited and there is a derasha, it would seem at first glance to be Biblical. Yet there are other reasons (elsewhere, but even here in Rav Ashi's offering of a reason for the institution) to assume it is a Rabbinic institution. If so, what we have here is a mere asmachta, prooftext support / mnemonic which is not really real and is not the true basis for the institution.

Yet, as I mentioned in the previous post, I think that several of these "asmachtot" may be treated as real derashot. However, the derasha is not why the individual should do it but rather why Chazal should institute a gezeira or takana.

Indeed, I would argue that this is what is happening in this instance. The gemara again:

Shmuel said: Because the Scriptures stated {Shemot 20:7}:

ז זָכוֹר אֶת-יוֹם הַשַּׁבָּת, לְקַדְּשׁוֹ.

7 Remember the sabbath day, to keep it holy.

Remember it from another day {Yom Tov} that comes to cause it to be forgotten.

That is, cause it do be remembered, in order to protect it from being forgotten due to another day that can cause one to forget it. By instituting this Rabbinic law, Chazal ensure that Shabbat is not forgotten in this instance, and thus fulfill זָכוֹר אֶת-יוֹם הַשַּׁבָּת, לְקַדְּשׁו -- make certain it is remembered, and thus sanctify it.