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Eruvin 51a

עירובין נ״א ע״א

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Topic

Setting שביתה at a distance, the source and shape of the 2,000-אמה תחום, and the poor man's עירוב with his feet

Overview

The amud opens with רבא's condition: a traveler may set his שביתה at a distant tree only if he could reach it by running before Shabbat. אביי objects from the משנה's words 'it got dark on him,' and the גמרא explains that this means only that he can no longer reach his house. In a story, רבה sets a שביתה for himself and רב יוסף under a famous palm tree that רב יוסף does not know. רבה supports this with רבי יוסי's ברייתא, though the גמרא says he used רבי יוסי's name mainly so that רב יוסף would accept the ruling. The גמרא then asks where the 2,000-אמה תחום comes from. רב חסדא answers with a chain of גזירה שוה links ending at the ערי הלוים, and the גמרא defends it against a challenge from the 1,000-אמה פסוק. Next comes a dispute over whether the תחום is a circle (רבי חנינא בן אנטיגנוס) or a square (רבנן, from רב חנניה's 'כזה'), and the square idea is applied to carrying ארבע אמות and to a pillar's width. Finally the משנה about a poor person making an עירוב with his feet is quoted. רב נחמן begins explaining the מחלוקת, and his explanation continues on the next amud.

Opening lines

אָמַר רָבָא:

Rava said:

וְהוּא דְּכִי רָהֵיט לְעִיקָּרוֹ מָטֵי.

And that is only when, if he would run to its base, he would arrive (before Shabbat).

אֲמַר לֵיהּ אַבָּיֵי:

Abaye said to him:

וְהָא ״חָשְׁכָה לוֹ״ קָתָנֵי!

But it teaches 'it got dark on him'!

The steps (27)

  1. Statementרבא: he must be able to reach the tree by running
  2. Challengeאביי: the משנה says 'it got dark on him'
  3. ResolutionDark only relative to his house
  4. StatementSecond version: dark only if walking slowly
  5. Statementרבה names a famous palm tree as their residence
  6. Questionרבה asks if רב יוסף knows the tree
  7. ProofRely on me: רבי יוסי's ברייתא
  8. Rejectionרבה only used רבי יוסי's name so רב יוסף would accept the ruling
  9. StatementBack to the משנה: someone who does not know a landmark
  10. QuestionWhere does the Torah write the 2,000 cubits?
  11. ResponseA ברייתא reads the 4 and 2,000 cubits into the verse
  12. QuestionHow do we know 'place' means 2,000 cubits?
  13. Responseרב חסדא's chain of word links leading to 2,000 cubits
  14. ChallengeWhy not learn from the 1,000-אמה פסוק?
  15. ResolutionLink 'חוץ' only to the identical word 'חוץ'
  16. ChallengeEven different words are linked elsewhere
  17. ResolutionUse the exact match when one exists
  18. StatementThe משנה says 2,000 אמה in a circle
  19. ChallengeA two-sided challenge to the circle view
  20. ResolutionThe word 'זה' limits square measuring to the ערי הלוים
  21. QuestionHow do the רבנן read the word 'זה'?
  22. Responseרב חנניה: all Shabbat measures are like this
  23. StatementCarrying ארבע אמות is measured including the diagonal
  24. Questionרבא's test: does a pillar need the diagonal?
  25. ResponseThe students answer from רב חנניה
  26. StatementThe משנה: a poor person makes an עירוב with his feet
  27. Statementרב נחמן: the dispute is about saying 'my place', since רבי מאיר holds an עירוב is mainly bread