Moreinu HaRav HaGaon Rav Moshe Dovid Tendler zt”l was many things: A posek and a professor; a rosh yeshiva with a PhD in microbiology; a synagogue rabbi and scientist. But for me, he was my rebbe muvhak, primary teacher.
For decades, Rav Tendler served with distinction as a rosh yeshiva at Yeshiva University’s Rabbi Isaac Elchanan Theological Seminary and professor of biology and Jewish medical ethics at Yeshiva College. He entered the yeshiva at the age of 13 in 1939 and, in his own words, “never left.” Yeshiva University’s motto of Torah U’Madda was his own personal mantra. But he would often quip that there should be “more madda in the Torah classes and more Torah in the madda classes!” He brought science into the beit midrash and Torah into the laboratory. Sophisticated sugyot were illuminated by scientific material and his biology classes were peppered with statements of Chazal.
A rare scholar, he was an expert in both Torah and science. And he saw no conflict between the two. For him, they lived together in perfect harmony. They complemented one another. He was equally at home quoting Galen as he was quoting the Rambam. Equally at home in the dalet amot, the domain, of the beit midrash and the four ells of the science lab.
His Torah was a Torat chayim, a living, breathing Judaism that engages the modern world and confronts its challenges. He believed that an understanding of science, technology and the metziut is indispensable to understand the Torah and perform mitzvot. He would often point to how Rav spent 18 months among the shepherds studying what types of blemishes on animals heal and which are permanent (Sanhedrin 5b); how Rabbi Zeira was hesitant to rule on issues of family purity without requisite knowledge of the physiology involved (Niddah 20b); and the Talmud’s critique of one who knows how to calculate the calendar based on astronomy and the constellations but does not, as such calculations are considered a “mitzvah” (Shabbat 75a). “There is wisdom found among the gentiles” (Eicha Rabbah 2:13), and for Rav Tendler, a thorough understanding of that wisdom is sine qua non for deciding Halacha.
Rav Tendler was an invaluable resource to his father-in-law, HaGaon Rav Moshe Feinstein zt”l. When Rav Moshe was posed with questions of medical procedures, or innovations in science and technology, he turned to his beloved son-in-law. Rav Tendler is quoted in tens and tens of teshuvot in the Igrot Moshe, providing the necessary medical or scientific information needed to pasken the shayla.
Himself a preeminent posek and pioneer in the field of medical Halacha, Rav Tendler ruled on the most difficult and delicate areas of Halacha: Complicated questions of pikuach nefesh (saving a life), end-of-life issues, organ donation, agunot, abortion and reproductive medicine. He answered them all with a surgical precision, a great finesse and with a great sense of responsibility. He had broad shoulders and garnered the confidence of the broad community, recognized as a leading authority.
In addition to his many accomplishments, he also developed a cancer drug he named Refuin. A Time Magazine article dated May 31, 1963 described how “the discovery made by Dr. Moses D. Tendler… took on an aura of romance because he spends only part of his time in the laboratory, the rest in his study as a Talmudic scholar.” Even Time Magazine couldn’t ignore this kiddush Hashem. As the Mishna he was fond of quoting states, “Lovely is the study of Torah together with worldly pursuits!” (Avot 2:2).
How many can boast that their rosh yeshiva discovered a cure for cancer?
Returning from the funeral of Rav, the Talmud (Berachot 42b-43a) records how his students sat by the river and ate. When they finished and wanted to bentsch, a question arose to which they had no answer. Rav Adda bar Ahavah stood up, rent his garment a second time and said, “Rav has died and we have not learned from him the laws of Birkat Hamazon!”
Now that Rav Tendler is gone, who will answer our questions? Who will provide us with direction and guidance in the most difficult questions of medical Halacha, innovations in science and advancements in technology?
His shiur was unlike any other in the yeshiva. Rav Tendler wouldn’t get lost in abstractions, pilpulim or lomdus (interpretation or study). Instead, his shiur was aliba d’hilchata, focusing on Halacha l’ma’aseh, the practical application of Halacha. The sugya would come to life, pirouetting off the page of the Gemara, as Rav Tendler would share real questions and cases he was personally involved in, drawing on years of experience as a posek. We would often look together at the teshuvot of his beloved shver, HaGaon Rav Moshe Feinstein zt”l, with Rav Tendler providing fascinating footnotes and important background information to the teshuva.
Rav Tendler defined Torah lishmah, the study of Torah for its own sake, as l’shem hora’ah, for the sake of being able to rule; to render psak Halacha. He would invoke Kiddushin 30a: “The words of Torah should be sharp in your mouth, so should someone ask you a question you will not stammer—instead, answer him immediately.” And he was critical of those who study in yeshiva or kollel for many years, but when asked how to make a cup of tea on Shabbos, don’t want to pasken.
It was not uncommon for me to be sitting with him in his office at Yeshiva University, or at his home in Monsey, and he would receive a phone call—usually from across the great expanses of the globe—on some serious matter. And it was also not uncommon for him to quickly gesture to me to pick up the phone and listen in on the conversation, so I could hear how he navigated the complex question.
He wanted his talmidim to be competent and confident in answering a shayla.
He was also the address when the answer was unclear, or the question too great for a newly-minted rabbi. We knew we could turn to him and he would guide us. One of the poskei ha-dor was just a phone call away, always magnanimous, always generous with his time.
It’s no surprise he was so generous with his talmidim, he loved us. Chazal compare the talmid-rebbe relationship to the parent-child relationship (Sifrei, Va’etchanan). This was tangible to anyone who merited to be a talmid of Rav Tendler. He treated us like his own children and our children like his grandchildren. Our smachot were his smachot, and our successes were his successes. He was deeply invested in his talmidim, and was so proud of their accomplishments. Together with his late Rabbanit Sifra a”h, he would open up his home to us for Shabbat, Yom Tov and Chanukah. And we talmidim didn’t call him Rav. We called him Rebbe.
Rav Tendler was a towering intellectual giant, but at the same time very down to earth and easily approachable. He was famous for his wry sense of humor. He possessed a sharp wit and biting sarcasm. Always quick with a comment or a comeback. Once when asked by a student if a certain decadent dessert made with dairy equipment can be eaten after meat, he scratched his beard and wondered aloud if it should be eaten at all, given just how unhealthy it is.
As a posek he could be unyielding, uncompromising and unapologetic. He lived the Torah’s charge to the dayan: “You shall not tremble before any man” (Devarim 1:17). Whether it was brain death, metzitza b’peh (direct suctioning) or ascending the Temple Mount, he was unafraid to take a controversial position, even at great personal cost. He strove for truth, often quoting the Maharshal’s comment that any distortion of the Torah is yehareg ve’al ya’avor, better to die than transgress (See Yam Shel Shlomo, Bava Kamma 4:9) or Rav Soloveitchik’s comparison of a posek who errs to a false prophet.
He had an illustrious career, spanning decades dedicated to Jewish communal life. As a rosh yeshiva and the rabbi of Community Synagogue of Monsey, he helped shape Orthodoxy in America in the 20th Century. He lectured around the world, spoke in the Knesset and testified before the U.S. Congress. His books and dozens of scholarly articles on the intersection of Halacha, science and medicine guided generations, and will continue to guide generations to come. He was blessed with arichut yamim, long life, and continued giving shiurim until his most recent illness made it impossible. He drew strength from his great love for the Torah and his great love for his talmidim. And he returned his soul to his Creator on Shemini Atzeret/Simchat Torah here in Israel, the day we celebrate our intimate relationship with Hashem and His holy Torah.
“From Moshe to Moshe, no one arose like Moshe.” Like Moshe Rabbeinu, Moshe ben Maimon and Rav Moshe Feinstein, Rav Moshe Tendler taught Torah to generations, connecting them with our mesorah. He was a living link in the chain of tradition and leaves a lasting legacy in the myriads of talmidim he taught and inspired.
יהי זכרו ברוךShimshon HaKohen Nadel lives and teaches in Jerusalem, where he serves as mara d’atra of Har Nof’s Kehilat Zichron Yosef and rosh kollel of the Sinai Kollel.
