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ERUVIN 51 (18 Iyar, Lag b'Omer) - dedicated by Avi and Lily Berger of Queens, N.Y., in memory of Lily's father, Mr. Benny Krieger (Chananel Benayahu ben Harav Yisrael Avraham Aba), zt"l, who passed away on Lag ba'Omer 5763. Mr. Krieger exemplified Ahavas Chesed, Ahavas Torah and Ahavas Eretz Yisrael.


1. Rava: A person may designate a tree as his residence for Shabbos only if he could technically get there before Shabbos.
2. The Gemara discusses the source for the law that 2,000 Amos from one's residence is the limit for the Techum Shabbos.
3. Rebbi Yishmael: A Gezeirah Shavah can be derived using words that are similar to each other.
4. Rav Acha bar Yakov: The prohibition against carrying four Amos in Reshus ha'Rabim is not literally four Amos.
5. Rav Nachman and Rav Chisda disagree about when Rebbi Meir and Rebbi Yehudah in the Mishnah (49b) agree with each other.


1. When the Mishnah (49b) states that saying, "My residence is at the base of that certain tree," is valid, it is only if he could run to the base of the tree and arrive there before the onset of Shabbos (even if he does not actually do so). However, if he could not possibly get there before Shabbos, his words do not take effect.
2. Rav Chisda explains that the teaching originates with the verse, "A man may not go out of his place on Shabbos." Through multiple derivations, Rav Chisda shows that the word "place" here refers to 2,000 Amos.
3. However, when there is a choice between deriving the Gezeirah Shavah from similar words or deriving it from identical words, it certainly should be derived from identical words.
4. Rather, the prohibition forbids a person from "leaving his space" in Reshus ha'Rabim. Since the Gemara earlier determined that a person's space is a four-Amah square (Daf 48, #3), a person is said to have left his space only if he carries diagonally across the entire square (i.e., the longest straight distance from one point in the square to another point in the square, which is five and three-fifths Amos).
5. For example, Rav Nachman says that everyone agrees that saying, "My residence should be in a certain place," is a leniency only for poor people or travelers. Rav Chisda contends that this is the case in which the Tana'im argue, and that the Tana'im agree that anyone, whether rich or poor, may say, "My residence is in my current place."

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