Sunday, June 13, 2021

Exploring Hilchot Eruvin - Jewish Action

Exploring Hilchot Eruvin - Jewish Action

Exploring Hilchot Eruvin

Typically, Jews study halachah for two reasons. Sometimes, they study it because they are interested in its practical application to their lives—witness the explosion of halachic literature on topics of Jewish law, from business to kashrut, from blessings and prayer to Shabbat and yom tov. At other times, Jews might study halachah for a more theoretical reason. Jewish laws—especially Biblical ones—capture an aspect of God’s plan and purpose for humanity (Rambam, Temurah 4:10). Hence, the study of even non-practical halachah serves an intellectual and spiritual purpose: it helps us understand our aspirations for humanity and the values we live by.

The laws of eruv construction fall into neither of these two categories. They comprise one of only a mere half-dozen sections of the Rambam’s Mishneh Torah that famously do not connect to any Biblical imperative (Keilim and three sections in the book of Kinyan are the others), and one finds it challenging to see in the rabbinic laws of eruv any part of God’s master plan for the universe. Moreover, since most eruvin are organized, supervised and checked by a very small subset of the population, the laws of eruv construction are hardly practical for the vast majority of the Jewish population. As a result, with the small exception of the three months every seven years when Eruvin is studied as part of the Daf Yomi, this aspect of Judaism largely resides out of sight and out of mind for most Jews, as it has been, sadly, for centuries (Shiyurei Knesset HaGedolah, Yoreh De’ah 245).

Rabbi Chaim Jachter and Rabbi Yosef Gavriel Bechhofer have each recently authored new or updated halachah handbooks on eruvin. Walking the Line: Hilchot Eruvin from the Sources to the Streets and The Contemporary Eruv: Eruvin in Modern Metropolitan Areas, respectively, provide a unique third reason to be motivated to learn this understudied area of Jewish law. Reading these books, one realizes that the study of eruv is at its core the study of community, and that the development of Jewish societies and Jewish living is best captured through the history of eruvin. Even if the reader is not interested in the practicalities of the two vertical posts and horizontal wire that become a theoretical door or wall for a community, he or she may be interested in the stories of Jewish communities that recur throughout both Rabbi Jachter’s, and to a lesser extent, Rabbi Bechhofer’s, books.

How is community life different in Israel, the Jewish State, as opposed to the Diaspora? The eruv gives a clue when we notice that eruv wires and posts are straighter in Israel because the Jewish, even if secular, government wishes to support Jewish living (Jachter, 202-205).

What are the implications of young Jews leaving their home communities for campus life? The eruv gives a clue when we consider the necessities of adopting possible leniencies on campus: the Yeshiva University eruv and its sagging wires (129-136), Yale University and the stringency of the Tevu’ot Shor (146-155), and Princeton University and the question of the horizontal wire that crosses the vertical posts instead of resting above them (141-145).

Jews today send their children to summer camps, and so eruvin must be built—for example, at Camp Morasha (with horizontal posts almost reaching the ground [107-108]).

More broadly, the story of eruvin is the story of Jewish communities on different continents (167-179); in environments ranging from rural (navigating the question of cornfields [156-160]) to super-urban (cities with more than a million residents [10-21]); weathering storms (233-239), price wars (resulting in fewer lechis [doorposts] needed [213-215]), and community strife (206-212); and, on the positive side, exhibiting community volunteerism (217-222).

The topic of eruv also captures the range of opinions between American Ashkenazim, Sephardim (with a different standard for a reshut harabim [public domain] 180-195), and Chabad rabbis (insisting on smaller tzurot ha’petach [doorframes] 196-201).

In a scholarly essay appended to the fourth revised and expanded version of The Contemporary Eruv (Bechhofer, 220-249), the author is explicit about this point: an eruv is a marker of a community more than it is an artifact of Jewish ritual or Jewish law. He stresses that the infrastructure of an eruv does not serve a political purpose or even a religious purpose. Instead, it marks secular public space. Thus, the study of the construction of an eruv is less a religious study and more a remark on the contours of a religious community’s physical space instead.

The presentation styles of the two works are slightly different and may appeal to different audiences. Though each work stands alone and is simultaneously erudite enough for a scholar yet accessible to the layman, they provide for different learning experiences. Rabbi Jachter’s work reads seamlessly, with few distracting footnotes and with illustrations on the page of the text when needed. Rabbi Bechhofer’s work may be preferred by a more scholarly audience, with long discursive footnotes, occasional lengthy quotations of the original Hebrew sources, and an appendix of more than 100 color photographs capturing the real-life nature of eruv infrastructure. In addition, the two rabbis use slightly different methodologies to reach their final halachic rulings. Both works cite all the relevant Acharonim; however, Rabbi Jachter concludes with the ruling of his rebbeim (Rabbi Hershel Schachter and Rabbi Mordechai Willig) on nearly every other page, while Rabbi Bechhofer quotes posekim of the previous generation and rules based on their consensus.

The two works are actually in dialogue with each other on many important, substantive issues. Rabbi Jachter devotes a major section to Rabbi Bechhofer’s objection to the “side top wire” (Jachter, 110-116), and another major section to Rabbi Bechhofer’s insistence that there be a vertical post on every utility pole (83-94) to which Rabbi Bechhofer responds in his fourth edition (Bechhofer, 177-180). Even when they disagree, however, the esteem the two rabbis have for each other is clearly demonstrated throughout each work. Rabbi Bechhofer reproduces Rabbi Jachter’s eruv guidelines and calls them “significant and essential” (194-219), and Rabbi Jachter quotes Rabbi Bechhofer’s earlier work with respect. Ultimately, the two works have the same goal in mind—the best possible Torah observance by the Orthodox Jewish community.

Both works are recommended to those looking to learn the basics of the laws of eruv construction in the Jewish community or those seeking to understand what it means to live in a Jewish community anywhere in the world in our current day and age.

Rabbi Dr. Yaakov Jaffe is the dean of Judaic studies at the Maimonides School and rabbi of the Maimonides Kehillah in Brookline, Massachusetts. 

Sunday, May 09, 2021

Friday, May 07, 2021

Kidneys Revisited

Some ten years ago I engaged in a sparring match on the question of כליות יועצות, Chazal's statement that the kelayos, apparently the kidneys, give counsel. My sparring partner, Rabbi Dr. Natan Slifkin, asserted that Chazal believed that thought takes place in the kidneys, not in the brain. I argued that this was a metaphor, as the two kidneys incline towards each other as if counseling one another. There were several post on both his and my blog going back and forth. See, for example,

One can also follow the search at

and look at the top results.

But, I recently learned Berachos 61a again:

ת"ר שתי כליות יש בו באדם אחת יועצתו לטובה ואחת יועצתו לרעה ומסתברא דטובה לימינו ורעה לשמאלו דכתיב (קהלת י, ב) לב חכם לימינו ולב כסיל לשמאלו

...תנו רבנן כליות יועצות לב מבין לשון מחתך פה גומר

and a new thought struck me.

I would like to suggest that kelayos are the term that Chazal used to refer to the two hemispheres of the brain. The term is a borrowed term, as the primary reference is to the kidney (first illustration), and only used by extension for the cerebral hemisphere (second illustration). Yet the sacrificial offerings of the kidneys may in turn be seen as symbolic of the two halves of the brain.

As of yet, I have no independent evidence for this hypothesis, but I wanted to put it out there and perhaps someone will find such evidence.


1. "Erasistratus described four ventricles in the brain, noting that the fourth ventricle under the cerebellum communicated with the third, whereas Herophilus seems not to have noticed the third ventricle: this may have been the first description of the cerebral aqueduct (Tsuchiya et al. 2015). He likened the cerebral gyri to the coils of the small intestine and, long before Thomas Willis (1664), he suggested that the extensive cortical surface of the human brain was in some way related to intelligence, …"

2.  "According to the theory of TCM [Traditional Chinses Medicine], the brain is an outgrowth of and is nourished by the kidney. Brain defects and deterioration of the brain may be prevented, limited, or halted by the ingestion of kidney tonics. And, the energy from the kidney, that is called kidney essence, can produce marrow including cerebral marrow, spinal cord, and bone marrow. As Huangdi's Classics on Medicine said: “the brain is sea of marrow” and “kidney stores essence to generate marrow” [15]. The cerebral marrow can nourish the brain and maintain the physiological functions of the brain. If the kidney essence is insufficient, the production of cerebral marrow will be reduced, leading to various symptoms, such as dizziness, amnesia, and retard response.

3. Both the brain and the kidney have a cortex and a medulla.

Monday, May 03, 2021

My 8th Siyum on Talmud Bavli, 20 Iyar 5781

Major hakoras ha'tov to the Hanhalah and eighth grade talmidim  at YBH for making the siyum such a memorable occasion. May we continue to be mechazek each other!

Sunday, May 02, 2021

Rav Dessler on Hitting Children

Rav Dessler's letter on hitting children.
Michtav Me'Eliyahu vol. 3 pp. 360-362.
An English translation in two parts is at:

Mavo HaTalmud part 1

After a three part series on Klalei Horo'oh - How We Rule in Disputes of Tannaim and Amoraim, we are now going to beginning of the Mavo HaTalmud and starting with the

Basic principles from the Mavo HaTalmud of Rabbi Shmuel HaNaggid with the Kitzur Klallim and other commentaries.

The Mavo is printed in the back of the Vilna Bavli Berachos and can also be found at

Information on Rabbi Shmuel HaNaggid can be found at:

Sunday, April 25, 2021

Rischa D'Araisa Season 3, Episode 3: The Kivelevitz Bechhofer News Hour: Two Dayanim's Perspectives on Recent Police Killings

Rischa D'Araisa Season 3, Episode 3:

The Kivelevitz Bechhofer News Hour:

Two Dayanim's Perspectives on Recent Police Killings


From a correspondent: 

 Rabbi Yosef Gavriel Bechhofer. I’m trying to understand your understanding of the Rambam’s יכול להצילו באחד מאבריו. You seemed to be saying that the מציל actually has to try a non lethal method before he uses lethal force. I understand this if the rodef is running after the nirdaf and there is time to try non lethal and if it doesn’t work, then use lethal. But in a case where you only have time for one (either lethal or non lethal) are you obligated to first try the non lethal method even if it means that if it doesn’t work, the rodef will be able to kill nirdaf? To me it seems like לא יכול להצולו has to be in estimation of the מציל in that situation and he doesn’t actually have to try non lethal method first. But you seemed to be saying otherwise on the podcast so I wanted to understand your position. Thanks. 

My replies:

1. Reb Boruch Ber in the Birchas Shmuel Bava Kamma #19 holds that the din rodef does not apply b'yachol l'hatzilo b'echad mei'eivarav. I think that the omek ha'pshat in that is like I have said, in that case you must try echad mei'eivarav first. 

Rav Charlap in Beis Zvul vol. 2, siman 2 #7 also writes explicitly that according to R' Yonoson ben Shaul (according to whom the Rambam paskens), that b'yachol l'hatzilo b'echad mei'eivarav there is no din rodef:

2. Rabbi Yisrael Rozen, in explaining the machlokes in the Gemara uses the same language that I used of hutra vs. dechuya.

3. An amazing Kovetz Shiurim:

 קובץ שעורים ח"א - מסכת פסחים דף מט/א (רא) דף מ"ט. בהא דממון מסור מותר, משום ק"ו, דגופו מותר ממונו לא כ"ש, קשה, דהא דגופו מותר הוא משום דהוי רודף, ומותר משום הצלת הנרדף, ואי לאו טעמא דהצלה גם גופו אסור, ולענין ממונו, הא איירי דאין בזה משום הצלת הנרדף ואין כאן ק"ו, והנה בתוס' סנהדרין ע"ג כתבו, דהא דאיצטריכו תרי קראי ברודף, הוא חד לרשות וחד למצוה, ואפשר, דטעמא דהצלת הנרדף הוא לענין המצוה, אבל לרשות א"צ לה"ט, אלא גזה"כ, דבשעה שהוא רודף אין לו דמים וגופו מותר בלאו טעמא דהצלת הנרדף, והא דאסור להורגו אם יכול להציל באחד מאיבריו אפשר, דאז לא מיקרי רודף, אלא האבר הוא הרודף, דדין רודף אינו תלוי במה שרצונו להרוג, דהא אפילו תינוק בן יומו מיקרי רודף, אם ההריגה תהא על ידו, וביכול להצילו באחד מאיבריו, ההריגה תהא ע"י האבר: 4

According to Reb Elchonon, in a case of yachol l'hatzilo the limb is the rodef, not the person! 

4. This sevara is similar to what I am saying:

 חבצלת השרון על בראשית פרק לב פסוק ח ואמנם יש להעיר על זה, דהלא לענין איסור רציחה אין פטור אונס, כי הוא מעבירות החמורות שיהרג ואל יעבור, וא"כ למה מותר לו לנרדף להציל עצמו ע"י הריגתו של הרודף, הלא כל היתר הריגת הרודף הוא רק משום שחידשה תורה שמותר להציל עצמו בנפשו של חבירו, אך פטור אונס לא מצינו לענין רציחה, ומאחר דבגוונא דיכול להצילו באחד מאבריו ליכא דינא דרודף ממילא אף דינא דאונס פקע, וצ"ע בזה: 4 

5. The Shoel U'Meshiv Mahadura Revi'a'a vol. 2 #50 uses a similar sevara in a different case, a kattan being rodef a kattan. My assertion is that the same sevara of mai chazis applies to any case of yachol l'hatzilo:


Tuesday, April 06, 2021

Site is back up and running, all links fixed: Rabbi Schiller and Rabbi Bechhofer

Site is back up and running, all links fixed 

Rabbi Schiller and Rabbi Bechhofer

"These are some of the greatest shiurim ever!" - DK, Passaic, NJ

Rabbi Mayer Schiller and Rabbi Yosef Gavriel Bechhofer

 A series of public discussions concerning Avodas Hashem and its various derachim. These discussions were held during MTA's Thursday night Mishmar on an occasional basis. The first two conversations of the 5767 school year were moderated by the Head of School at the time.

Friday, April 02, 2021

Maror and Chazeres

The obvious question:
Why both maror and chazeres?


ותחת המרור החזרת שעושין כורך, מחמת שינוי הלשון, דבתחילה קורא אותו מרור ואח"כ חזרת (וכ"ה ג"כ בפע"ח, מ"ח, סי' קול יעקב, סי' הרש"ר), יש נוהגין שלא ליקח מין אחד למרור ולכורך, ואפילו במקומות שנמצא סאלאט אינם עושים הכל מן סאלאט, וטעמם אולי אין בקיאין בחמשה מינים שבמשנה (פסחים לט, א) לכן יוצאים אכילת מרור בירק מר. ולא דקו דא"כ יש לאכלו בלא ברכה, וכמ"ש בשו"ע אדה"ז ס' תע"ג סל"א. אבל באמת מצוה להדר אחר חזרת (פסחים שם), דהיינו סאלאט, שעיקר המצוה בה (שו"ע סתע"ג ס"ל) ואין חילוק בין מרור לכורך. והא דשינה בלשונו הוא כי אם הי' כותב ותחת המרור המרור שעושין כורך (ועדמ"ש בשו"ע אדה"ז סכ"ו) היו טועים לומר שלכורך יותר טוב ליקח המין הנקרא במשנה מרור, ובאמת מצוה בחזרת (שער הכולל). והתירוץ תמוה, דא"כ גם עתה יש מקום לטעות, דלמרור יותר טוב ליקח מרור שבמשנה. ולהוציא מכל טעות הול"ל: "תחתיהם באמצע החזרת ותחת כו' ותחת החזרת החזרת שעושין כורך". ואולי יש לתרץ שינוי הלשון, כי הנה התבות "מרור", "חזרת" כמה רמזים ע"ד הסוד בהם - וכמ"ש בפע"ח וקהלת יעקב - ורמזי תיבת מרור שייכים יותר לבחינת מרור שעל הקערה ורמזי תיבת חזרת - לכורך. ולכן בשו"ע אדה"ז שהוא יותר ע"ד הנגלה לא קפיד לשנות, וצ"ע. - ואנו נוהגין ליקח חזרת (סאלאט) ותמכא (חריין) שניהם-הן למרור והן לכורך

As to the remazim, I would suggest as follows:

Maror in gimatriya is מות - death.

Chazeres in gimatriya is תורה+the four letters of the word Torah.

Maror corresponds to Tiferes and Chazeres to Malchus.

Maror is the way in which the Divine conduct of the world is usually manifest. But, just like death being טוב מאד (Bereishis Rabba 9:5), so too this hanhogo is for our benefit. Ultimately, the tikkun of the maror is the bechinah of Yaakov Avinu, since יעקב אבינו לא מת (Taanis  5b) - even though חנטו חנטייא וספדו ספדיא - because death is the illusion of this world, a very realistic illusion, but an illusion nonetheless.

As Rabbi Yochanan answer there, מקרא אני דורש.

The tikkun for death from our side is through the Torah we expound. Specifically, the Torah we "write" - the justification for including the letters of Torah in our gimatriya - Torah She'B'Al Peh.

Our tikkunim occur in Malchus, which is our reflected light - אור חוזר - hence chazeres, which, in the form of lettuce, is "sweetened" maror, and the bechinah of חסה - חס ה - a glimmering of chesed

Of course, that tikkun is fully accomplished by korech. May it be possible to achieve that full tikkun במהרה בימינו אמן!

Tuesday, March 30, 2021

Chodosh and Yoshon in Chutz La'Aretz, Five Part Series Playlist

Chodosh and Yoshon in Chutz La'Aretz
Five Part Series Playlist
Following the reasoning of the
Arukh HaShulchan
text included in screen shares.

Friday, March 26, 2021

Machine Matzo and Murder


The Controversy surrounding machine matzo is well known. See:

However, it struck me this morning that if you hold machine matzo is invalid, you probably could never impose the death penalty on someone who commits murder with a gun!

At "best" it may be garmi.

It seems that it would not be considered koach rishon. Even if it were, in order to be liable you may have to have first immobilized the victim.

Best just to hold that machine matzos are suitable for the mitzvah.


Thursday, March 25, 2021


 אמרו לו א"כ יהא יודע בשבעים לשון בא גבריאל ולימדו שבעים לשון לא הוה קגמר הוסיף לו אות אחת משמו של הקב"ה ולמד שנאמר (תהלים פא, ו) עדות ביהוסף שמו בצאתו על ארץ מצרים (שפת לא ידעתי אשמע) ולמחר כל לישנא דאישתעי פרעה בהדיה אהדר ליה 

They said to him: If that is so and he is a child of royalty, he should know the seventy languages that all kings’ children learn. The angel Gabriel then came and taught him the seventy languages, but he could not learn all of them. Gabriel then added one letter, the letter heh, to Joseph’s name from the name of the Holy One, Blessed be He, and then he was able to learn the languages, as it is stated: “He appointed it in Joseph [Yehosef] for a testimony, when he went forth against the land of Egypt, the speech of one that I did not know I heard” (Psalms 81:6). And the next day, when he appeared before Pharaoh, in every language that Pharaoh spoke with him, he answered him.

Why specifically the extra Heh? Because the Heh consists of a yud and a daled =14. The Heh itself =5.


Tuesday, March 16, 2021

Comments on my 6th Grade Report Card

I have been told by students and parents that the comments on my 6th grade report card can be a source of chizzuk. Blue is Limudei Kodesh, green is Limudei Chol. (My English name is Robert.)

Monday, March 15, 2021

Quoted on Headlines...

At 44:46, Rabbi Moshe Taub quotes me as a posek that he brought in to help plan the Buffalo eruv. The quote is not about eruvin. Something that eventually made it into

Thank you to Reb Ari Brandwein for bringing it to my attention!

Sunday, March 14, 2021

Important Historical Documents from West Hempstead 1978

 To preserve for posterity:

Rav Dessler on Shittas Frankfurt vs. Shittas HaYeshivos part 3

The letter to Gateshead on the matter of starting a mens' teachers seminary in the yeshiva.

Michtav Mel'Eliyahu vol. 3 p. 355. Part 3.

Includes Prof. Zev Lev's response.
Summary and conclusion

Motzi Shem Ra on Reb Chaim Kanievsky?


In the Divrei Si'ach for Tetzaveh-Purim the following paragraph appeared:

In the Vayakel-Pekudei issue the following clarification appeared:

There is nothing of the sort in the Yerushalmi:

ירושלמי מגילה פרק ג הלכה ז
רב אמר צריך לאמר ארור המן ארורים בניו
א"ר פינחס צריך לומר חרבונה זכור לטוב

However, in the Ahavas Tziyon v'Yerushalayim we find:

see also


but it is not a Yerushalmi, rather some Rishonim in the name of the Yerushalmi

Their version of the Yerushalmi
is difficult to reconcile with
V'gam Charvona zachur la'tov;

see the attempt at a resolution at