Rabbi Moshe Tendler – Memories from a Shtender Boy


On September 28, 2021, over the holiday of Shemini Atzeret, my teacher R. Moses Tendler passed away. Due to shock and the timing of the Jewish holidays, it took some time for me to formulate coherent thoughts. I will leave it to others to discuss R. Tendler’s indelible legacy in the Jewish world and instead I would like to share some personal experiences.1

The Shiur

I joined R. Tendler’s shiur in the second semester of the 1996-1997 academic year. When I had arrived at YU for the fall semester of 1996, I didn’t know much about the shiurim and went to where I was assigned without objection. The shiur was fine, but I didn’t feel satisfied at the time. I went to switch to R. Tendler because both my father and uncle had a long history and relationship with him.

Although shiur selection was ultimately up to the student, administrators provided suggestions. In my case, I was actively discouraged from joining R. Tendler’s shiur on the grounds that his shiur at the time, “didn’t attract the best students.” What this meant was that for the most part the students in R. Tendler’s shiur were neither the strongest in terms of Talmud skills nor the most serious in improving them. In some cases, students only joined the shiur in the hopes of securing R. Tendler’s recommendation for med school down the line.2

These comments were in no way intended to be a knock against R. Tendler but rather expressions of concern that I would not be able to find a good havruta. I replied that I could learn far more from a great teacher than a great havruta. The administrator trusted me enough and signed me through.

Truth be told, the reputation for R. Tendler’s shiur was not entirely undeserved. I don’t know how many people registered for the shiur, but it was clear only a fraction attended on a regular basis and many of those who did bother to attend chose to silently blend into the back while hoping they wouldn’t snore. R. Tendler was not unaware of these individuals, sometimes referring to them as those who “held up the back wall,” or in more cynical moments, “clinical proof for brain death.” For those who didn’t bother attending at all, on the final day of my first semester in his shiur he stood by the door cordially greeting students, “Hello, my name is Rabbi Tendler. Welcome to the shiur, have a bechina...” 

On the other hand, those who did come to learn formed a neat semi-circle around his desk and we didn’t just learn from R. Tendler but we engaged with him. Instead of having one good havruta, it was like having a havruta of 6 people with R. Tendler.

R. Tendler had little patience for sycophants. He’d much rather someone engage with his teachings and argue in a way that showed one respected his view enough to understand it well than be flattered by toadies. R. Tendler recognized the difference between the superficial mimicry of what certain cultures perpetuated and genuine kavod.

Because I tended to get to shiur early, I was able to serve R. Tendler in the unofficial capacity of “shtender boy” being responsible for setting up R. Tendler’s lectern before shiur and locking it away afterward. I considered this a rare opportunity for a proper act of shimush ha-Rav.

Upon graduating from Yeshiva College and moving on to semikha, I spoke with R. Tendler about switching shiurim, something which he also thought was a good idea. It wan’t that I was done learning from R. Tendler, but he recognized the importance of learning from multiple teachers (see Avoda Zara 19a). Leaving his shiur by no means meant an end to our relationship. We stayed in regular communication for years after my graduation. My father insisted on visiting or calling him before every Yom Tov (see Rosh Hashana 16b) and I’d always try to pop by when I found myself back on the YU campus.

Memorable Moments

R. Tendler was one to speak his mind and speak his mind bluntly.3 While this trait undoubtedly led to some uncomfortable exchanges, there were also many memorable moments. Here is just a small sample of what I can still recall many years later.

R. Tendler wasn’t concerned with his reputation among the other Roshei Yeshiva at YU. He once remarked that even if he gets fired from his Rosh Yeshiva position, they can’t get rid of him because he had tenure from his position as a professor in the Biology department.

In the Winter 1987 edition of Tradition (22:4),  R. Herschel Schachter and R. Tendler published opposing articles regarding the kashrut of certain types of vinegar.4 R. Tendler’s introduction is worth quoting in full as it is exemplary of both his methodology and his personality.

As vinegar to the teeth and as smoke to the eyes, so is the laggard to them that sent him” (Proverbs 10:26). In this imagery, King Solomon suggests that failure to fulfill responsibilities with vigor and intelligence leads to confusion and frustration. The torch that was to dispel the darkness often produces a smoky flame that smarts the eyes and blurs the vision. The vinegar intended as an appetite stimulant sometimes suppresses appetite when it dulls the teeth. The recent finding that vinegar produced from alcohol distilled from wine had mistakenly been used to produce kosher food products, caused much consternation within the Torah community. Much of this dismay resulted from the failure to properly apply the halakhic process to elucidate the problem. The purpose of this presentation is to demonstrate the methodology that must be applied when scientific and technological data are evaluated for halakhic import.

The Anatomy of a Responsum: The Kashruth of Vinegar Produced from Wine Alcohol.” Tradition 22:4, 1997. p. 47

R. Tendler concludes that vinegar made from non-kosher wine is only permissible if it was done unintentionally. I asked R. Tendler privately why he reached this particular conclusion because based on the substance of his key arguments even vinegar intentionally made from non-kosher wine should be permissible. He replied that I was right but he got so much flack for his position at the time that he couldn’t say anything more in public.

In a private discussion regarding the permissibility of turkey, R. Tender conveyed a classic truism, “We follow the Ramo except when we don’t.”

R. Tendler would often share cases that came up in his beit din. One notable instance involved a business dispute between two partners. When R. Tendler inquired as to the nature of their business, a litigant replied that they purchased wristwatches and replaced their faces before resale. To which R. Tendler responded, “Oh. So you’re counterfeiters” and threw them out of his beit din.

R. Tendler recalled one year right before Yom Kippur a Syrian woman came to his house distraught that she didn’t do kapparot with a live chicken yet and she was convinced that if she would not do so before Yom Kippur that she would certainly die during the year.

R. Tendler cited this example as a useful heuristic for evaluating when segulot, simmanim, and superstitions shift from being innocuous to being idolatrous. As he put it, the more seriously one believes in them, the more halakhically problematic they get.

I blogged this story a long time ago, but it’s worth repeating here. My first nephew was born with a bit of jaundice which required delaying the bris for a bit. When R. Tendler asked about it, we had the following exchange:

Me: We don’t know when the bris will be yet. It depends on the Bilirubin numbers
R. Tendler: What are the Bilirubin numbers?
Me (innocently): Oh, those are the numbers that tell you how much jaundice the kid has.
It is at this time that I’d like to point out that R. Tendler has a PhD in biology, teaches bio in the college, and lectures extensively on medical ethics.
R. Tendler: I know what the Billirubin numbers are, I want to know what the Billirubin numbers are.

To elaborate a bit on this exchange, I had to explain what bilirubin numbers were so often to regular people that it just came naturally. And while even back then it was completely on-brand for me to answer for comedic value, this was absolutely not something I would do intentionally with R. Tendler.

The only time I saw R. Tendler eat in the college cafeteria happened to have been on a day the Roshei Yeshiva declared a fast day.5 I still can’t tell if this was a coincidence.

Someone once asked R. Tendler about kashering one’s refrigerator for Pesach. R. Tendler replied:

Of course you can kasher your fridge for Pesach. But why would you want to? What the Hell goes on in your fridge? Does it get yad soledet? If it gets yad soledet YOU NEED A NEW FRIDGE!

R. Tendler gave the absolute best mussar for college students. He chastised us for not spending more time in the library because, “When else in your life are you going to have the time to just sit and read?” Also he couldn’t understand why we wouldn’t take more advantage of YU’s facilities, the swimming pool in particular.6

R. Tendler was not a fan of genetic testing services that only said if a couple was compatible but did not share the results with individuals.

R. Tendler didn’t understand why there were separate shiurim for men and women. If anything, shiurim were the best place to meet a future spouse. 

R. Tendler endorsed donating blood, but he wasn’t thrilled that the same students tended to donate each time. In his view, the Roshei Yeshiva should have encouraged the entire student body to donate twice a year, which would give the blood bank a greater supply with less stress on individual students.

Before YU completed construction on new faculty offices, R. Tendler’s office was next to the bio lab in the basement of Furst Hall. One day I noticed a few big boxes outside his office for a new computer and monitor. I asked what they were for and he responded that apparently the office thought he needed a new computer. When I asked why they hadn’t bothered setting it up, he replied that they couldn’t set up the new computer until they got in security cables that would secure the computer and monitor to the desk. 

I pointed out that if theft was such a concern, it was a whole lot easier for someone to come and steal the computer and monitor while they were sitting unprotected in their unopened factory packaging. To which R. Tendler simply shrugged and smiled.

R. Tendler would sometimes slap me upside the head if I was being particularly cheeky. One such occasion was when he complained about women shaking lulav and etrog in public by the kotel. I asked what the problem was because if it’s permissible there’s no reason why it couldn’t be done in public and if the problem is the beracha levatallah for saying a beracha on a mitzvat ase shehazeman gerama then it’s the same issur for all women who shake lulav in private.

Memorable Teachings

Stories aside, here are some of the memorable teachings I learned from R. Tendler that stayed with me for decades

Eved Ivri as Rehabilitation

My first semester in the shiur we studied Kiddushin, specifically the rules of the eved ivri, the Hebrew slave. What I remember most was his framing of the Hebrew slave as an act of rehabilitation for the ne’er do wells of society. Rather than imprisoning thieves or debtors, the concept of the eved ivri was to place individuals in the households of the righteous where they would be taken care of, to the point where the Talmud states, “one who acquires a Hebrew slave acquires his own master” (Kiddushin 20a) The person works for six years, after which receives a form of severance pay.

Additional details preclude the eved ivri from being taken seriously as a morally viable option today. But R. Tendler’s point was that for its time, the institution could be seen as relatively progressive.

Making Room for God

Minha is the hardest prayer. Shaharit and ma’ariv can be integrated into one’s daily schedule; daven shaharit as part of one’s morning routine and ma’ariv before one goes to bed. But minha requires consciously interrupting one’s day to make room for God.

Confront Challenges

The question of how to handle biblical criticism loomed large at Yeshiva University. On one hand, to be perceived as an institution of higher learning, let alone offer graduate degrees in biblical studies, meant engaging with the prevailing scholarship. On the other hand, many of these ideas are oppositional to the traditional religious paradigms of the Yeshiva.

Many at YU took the approach of avoidance or suppression. After all, the easiest way to deal with a problem is to pretend it doesn’t exist. R. Tendler, however, took the opposite approach in that he wanted biblical criticism to be taught at YU. This was not because R. Tendler embraced or endorsed biblical criticism or because he had some mission to reconcile biblical criticism with Judaism.7 Rather, R. Tendler recognized that people were going to learn about biblical criticism at some point. His position was that if the students were to learn biblical criticism at YU, then the Roshei Yeshiva have an opportunity to respond. This doesn’t mean they’d be successful or convincing, but at least they’d have a chance to offer their point of view.

Always Speak to Reporters

R. Tendler would often complain in class when he got misquoted by a reporter or have a position misrepresented in the media. One time I asked why he continued to speak to reporters if they do such a lousy job and cause him so much aggravation. 

R. Tendler replied you have to give quotes to reporters for two reasons. First, if you don’t speak to reporters, then someone else will. As long as you keep the lines of communication open, there’s a chance the reporters will get it right. Second, having positive relationships with reports increases the odds of getting an important story covered that might otherwise have gone unnoticed.

For this reason I was always grateful to assist reporters who would call asking for religious or halakhic background for a story because it gave me the opportunity to help minimize misinformation.8

Embrace Aggadah

Aggadic passages in the Talmud aren’t always taken seriously in shiurim to the point where it’s not uncommon for rabbis to skip them entirely. R. Tendler’s approach was, “If they thought it was important enough to include it, it’s important enough for us to learn.” 

Every Thursday R. Tendler would teach from Midrash Rabbah. His approach was not to treat the midrash as literal or historical nor did he speculate on potential hidden meanings in the text. Rather, R. Tendler would always ask, “What’s the point of the midrash?” in an attempt to figure out the intended lessons of a particular teaching.

This is the approach I followed in my shul when I would teach midrash every Friday night, and in my weekly podcast on midrash, named after R. Tendler’s methodology.

Know What You’re Talking About / Do Your Homework

One of the most recurring themes in R. Tendler’s teachings was that one shouldn’t issue halakhic rulings pertaining to areas in which they have no expertise. While this ought to be a reasonable requirement, many rabbis overestimate their competence and issue incorrect decisions. This can be due to a lack of knowledge in either halakhah or the reality of a situation that requires a halakhic decision.

For example, R. Tendler believed that someone who doesn’t know animal biology should not pasken tereifot since without knowing the science one cannot know which wounds would be fatal. Another example would be his disagreement with his father-in-law R. Moshe Feinstein regarding the permissibility of Norelco’s “lift-and-cut” shavers. Based on the “Madison Avenue” presentation (to use R. Tendler’s words), these shavers would be prohibited because they function like straight razors. However, when R. Tendler took them apart to see how they worked, he determined that they are permissible because in reality they operate like scissors (with the hair breaking against a fixed bar). 

This also applies to arguably R. Tendler’s greatest and most controversial contribution in his ruling that brain death constitutes death according to halakhah regardless of whatever organs are maintained by medical machinery. Without getting into the details of his opinion, R. Tendler — who held a PhD in biology from Columbia University — deeply resented having to argue the science with rabbis who didn’t go to college.9

Safek Lehumra as the Avoidance of Pesak

How halakhah deals with doubt and cases of uncertainty is a fascinating and complicated subject far beyond what I can discuss here.10 However, R. Tendler observed a tendency among certain rabbis who were uncertain of what the halakhah should be in a particular instance would rule stringently in order, “to be on the safe side.”

Setting aside any potential negative consequences of this “safe side,” according to R. Tendler, this sort of reflexive ruling was not a psak but rather the avoidance of psak. Rabbis who for whatever reason don’t know how to answer a question should either put in the time and research to figure out an answer or defer to someone else who does.11

Passover as Finding God

One of the highlights of R. Tendler’s shiur was his annual pre-Pesach discussion. My father would routinely make time for a special trip up to YU to hear it and I did my best to attend even years after I had graduated. Sadly, I don’t remember every teaching, but R. Tendler’s main theme was that Pesach is about seeing God intervene in the natural world. The contemporary challenge of seeing ourselves as having left Egypt is to be mindful of the hand of God in the world, or at the very least, our own personal experiences.

Final Thoughts

It is never easy to lose a teacher and mentor and combined with last year’s passing of Haham Jose Faur I have lost two in as many years. While I have never subscribed to the axiomatic principle of a “declining of generations,” it is difficult to compare the caliber of my teachers with those of more pronounced influence today. The best we can ever hope to do is endeavor to perpetuate the best of their traditions.


  1. Note: All experiences are based on my time as an undergraduate at Yeshiva University from 1996-1999. Please be mindful that YU protocols may have changed since then.
  2. I should note that other shiurim also attracted students for less than spiritually sincere reasons such as the social prestige of being able to say, “I studied with Rabbi X.” Such statements could be critical for shidduchim.
  3. I’ve heard several people describe him as one who, “shoots from the lip.
  4. I discussed this article with R. Avraham Bronstein a while back including my delight at seeing chemical equations printed in a religion journal.
  5. For some reason that’s been lost to history.
  6. R. Tendler was an avid swimmer and on occasion we did laps at the same time.
  7. Or if he did, I’m unaware of it and I welcome anyone providing details to the contrary.
  8. I once spent an hour and a half on the phone with a reporter essentially giving a private shiur on a controversial topic. I was as pleased with the article as I was with not being quoted.
  9. A common response I’ve heard to this objection is that rabbis could simply learn what they need from experts in the field and decide accordingly. Of course, this is how education always works, provided one sufficiently understands the material. Furthermore, I’ve noticed that many of those who believe they can pasken life-and-death issues from listening to one doctor are notoriously protective against people paskening halakhah
  10. For one recent study, see Moshe Halbertal’s The Birth of Doubt: Confronting Uncertainty in Early Rabbinic Literature.
  11. This did not apply to situations where decisions had to be issued immediately due to time constraints, in which case, there are established halakhic guidelines for dealing with uncertainties such as being strict regarding biblical laws and lenient regarding rabbinic laws.
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