Are tehumin de-orayta?

The third through fifth chapters of Massekhet Eruvin discuss the laws of eruvei tehumin, "merging of boundaries." On Shabbat you may not leave your tehum, or boundary, defined by your location at the onset of Shabbat or by a designated eruv. You get your full domain, such as your city, plus two thousand amot beyond your domain.

Is the prohibition of leaving your tehum biblical or rabbinic?

The Mishnah in Sotah on 27b presents a mahloket tanna'im:

בו ביום דרש ר' עקיבא: +במדבר לה+ ומדותם מחוץ לעיר את פאת קדמה אלפים באמה וגו', ומקרא אחר אמר: +במדבר לה+ מקיר העיר וחוצה אלף אמה סביב, אי אפשר לומר אלף אמה שכבר נאמר אלפים אמה, ואי אפשר לומר אלפים אמה שכבר נאמר אלף אמה, הא כיצד? אלף אמה מגרש, ואלפים אמה תחום השבת; ר' אליעזר בנו של ר' יוסי הגלילי אומר: אלף אמה מגרש, ואלפים אמה שדות וכרמים.

Rabbi Akiva gives Numbers 35:5 as a biblical source for a tehum Shabbat of two thousand amot. It happens to be a pasuk dear to ba'alei keri'ah for its karnei parah. Thanks to this mishnah, the concept of biblical tehumin is referred to throughout the Bavli as tehumin aliba de-Rabbi Akiva. Rabbi Eliezer son of Rabbi Yosei ha-Galili reads the verse differently, and the Gemara on 30b explains the dispute as based on whether tehumin are de-orayta or de-rabbanan.

There other tanna'im quoted in the Bavli who say that tehumin are de-orayta, such as Rabbi Hiyya on Eruvin 17b and Rabbi Meir on Eruvin 35b.

How widespread is this view in the Gemara? We have a mahloket rishonim.

“Then let God compare it to nevelah!”

Since my last post, Daf Yomi has moved on to kil’ayim, poletet shikhvat zera, mattan Torah, back to shi’urim for hotsa’ah, and now has begun Perek ha-Matsnia on 90b. But this blog is still stuck on the objection of the Gemara on 82b,

ולוקשה רחמנא לנבלה!

This seems like an important point for the Talmud Bavli’s view of Torah she-ba’al peh, so I’m going giving it at least one more post.

The background is that Rabbi Akiva and the Sages disagree on whether the impurity of an idol works like that of a niddah or like that of a sherets. Each quotes a biblical verse for support. The rishonim understand the impurity of idols to be a rabbinic decree, so those verses are really asmakhtot, not sources. But then Rabbah qualifies the Sages’ opinion so that the impurity of idols is more like that of a nevelah than a sherets. The Gemara objects, “Then let the Merciful One [in the Torah] compare [the impurity of idols] to nevelah!”

Why does the Gemara expect the Torah to match a much later rabbinic decree?

How far does borer go?

One of the 39 melakhot in the mishnah on 73a is borer, “separating” a mixture of waste and food. This is one of the melakhot in siddura de-pat, the process of making bread.

In general, as the rishonim learn from Shabbat 74a–b, you may only select from a mixture under three conditions: (1) you remove the food from the waste, and not vice versa; (2) you remove the food by hand; (3) you remove it for immediate eating. When any of these conditions are missing, a penalty of karet is at stake. Each condition is very detailed, and I don't plan to cover them here.

One of the major questions with borer is how far its application goes. What kinds of mixed items are included in the prohibition? Just waste from food? Or even forks from knives?

At one extreme, there is the Talmud Yerushalmi, Shabbat 7:2, which quotes Rabbi Yudan's limited view of borer:

אמר רבי יודן יש שהוא בורר צרורות כל היום ואינו מתחייב יש שהוא נוטל כגרוגרת ומיד מתחייב היך עבידה היה יושב על גבי כרי וברר צרורות כל היום אינו מתחייב נטל לתוך ידו כגרוגרת ובירר חייב

It sounds like the only way to transgress borer is to clear the very last stone from a pile of grain. You have to entirely purify the food from its waste. Unlike what happened with zoreh, this is a case where you'd be happy for the Rema to pick up the Yerushalmi, at least if you like kulot.

At the other extreme, we have the “great question” of Rabbi Yehiel Michel Epstein, in Arukh ha-Shulkhan, O"H 319:8. He assumes that borer applies to literally “everything,” even a collection of non-food items. Were it indeed so, he objects, “we could not find our hands and feet!”

The Yerushalmi’s view of zoreh

One of the thirty-nine melakhot listed on Shabbat 73a is zoreh, winnowing. The Gemara at the bottom of 73b asks why this is necessary as an av melakhah:

היינו זורה היינו בורר היינו מרקד! - אביי ורבא דאמרי תרוייהו: כל מילתא דהויא במשכן, אף על גב דאיכא דדמיא לה - חשיב לה. וליחשב נמי כותש! אמר אביי: שכן עני אוכל פתו בלא כתישה. רבא אמר: הא מני - רבי היא, דאמר: אבות מלאכות ארבעים חסר אחת, ואי חשיב כותש - הויא ליה ארבעים. וליפוק חדא מהנך ולעייל כותש! - אלא מחוורתא כדאביי.

The Talmud Bavli understands zoreh as fundamentally the same as borer and merakked. Rashi explains that all of them are about separating food from waste:

היינו — כמו הי ניהו, כלומר דמפליג להו תנא דמתניתין לתלת, והלא כולן מלאכה אחת הן דמפריש אוכל מן הפסולת.

But on the other hand, the Talmud Yerushalmi understands zoreh as altogether different:

רקק והפריחתו הרוח חייב משום זורה וכל דבר שהוא מחוסר לרוח חייב משום זורה

“A keli sheni cannot cook”

Disclaimer: nothing in this post should be taken as practical. As Rav Eliezer Melamed explains,

התשובה הכללית, שבכלי ראשון הדבר אסור ובכלי שני מעיקר הדין מותר, אולם בפועל רק בכלי שלישי מותר.

In general, even though putting food in a keli sheni is permitted in principle, in practice we often allow only a keli shelishi. This post discusses the principle, not the practice.

Why is a keli sheni different from a keli rishon? Isn't possible to have a keli sheni that is just as hot as a keli rishon and cooks food just as easily?