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April 19, 2014 / 19 Nisan, 5774
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‘Kzayit’: Rashi Almost Certainly Never Saw an Olive


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Before you eat your k’zayit of matza at this year’s seder, you might pause to consider what you are about to say about yourself, and what message you are about to send to your family and friends.

I can tell you what message I will be sending: that Torah and Halakah are as real as it gets.

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About the Author: Rabbi David Bar-Hayim is the head of Machon Shilo, a centre of Jewish learning in Jerusalem dedicated to the exposition and dissemination of Torat Eretz Yisrael. The teachings of Rabbi Bar-Hayim may be found at www.machonshilo.org

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38 Responses to “‘Kzayit’: Rashi Almost Certainly Never Saw an Olive”

  1. Yosef Chiger says:

    Kol Hakavod to Rav Bar-Hayim. Very well said.

  2. Stefan Kirschner says:

    HaRav bar Hayim is one of the most important thinkers of the century as am Yisrael returns to its land.

  3. Nncy Kramer says:

    I liked this rabbi’s auccinct and well constructed arguments. It could certainly make the Seder/s so very much mre pleasant not to stuff oneself out f a misconception of what makes a kayzaith and concurrently makes our stomachs distended not t say what it des to the rest of us for days to come.

  4. Beyond asking how big an olive really is, perhaps we should ask a deeper question: Why did Chazal choose the olive as the halachic standard, and whether it is still a relevant standard today?

  5. Yitz Rephaeli says:

    To ZK: The volume of an olive is a straightforward, readily apprehended amount which any person can judge in an instant. See the Mishnah in Kelim 17:6. I’m guessing that you feel the amount should be updated to, say, 5cc. Most people cannot look at a piece of food and judge whether it is 5cc or not. They would have to measure. Chazal did not think that the Torah was given only to those who can measure. It is for all Jews, and it is supposed to be simple and seamless. A kezayis is as simple as it gets.

  6. In many ways orthodox judaism is broken and beyond repair
    And lacks resemblance to what we once and once believed. Rabbinic judaism of today is largely focused on very exact detailed actions with little meaning behind it

  7. Nony Sadek says:

    so, what were your previous beliefs?

  8. Ron Aaron says:

    There's a reason I follow halakha lema`ase like the Rambam

  9. Avi Kessner says:

    Still seems pretty relevant to me. It's the smallest amount you eat when you "have a bite"

  10. Rim Alagiy says:

    There is absolutely nothing fascinating about the unfortunate continuation of R' Bar Chayyim's Napoleon complex, with another article which purpose is to state "Bar Chayyim is teh smartest and most knowledgeable man in the Universe, while all Rishonim are retarded idiots who don't even know how an average olive looks". Truth is, all rishonim had an idea how olives look like, they just didn't know what "Zayit Agori" mentioned in Mishnah Kelim, whether it's a specified species or the average olive, and thus chose to deduce the shiur from the size of beit blia, which is approximately two kazayit and one kabeitza (E"E Kritut 14a – Yoma 80a). There are absolutely HUGE olive species. Perhaps BH knows less about the fruits of Eretz Yisrael than Baalei Hatosefoth in France.

  11. Sarah Kaye says:

    This is a rip-off of Rabbi Natan Slifkin's article written a few years ago.

  12. I'd rather read the original then. Have you got a link to it?

  13. Oh. Thanks. I didn't notice that link in your original status when I commented.

  14. Yitzi Lefkowitz says:

    I happen to have been reading the work of both Rabbim for years. This is not a rip off of either by either. Ever heard the saying, "Great minds think alike" Please be more careful in your comments about other people.

  15. Yitzi Lefkowitz says:

    Really? I can't event take you seriously. You being with insults then you insist on going to tangents to make your point. Consult the relevant sources.

  16. How would you describe the volume of an object in such a way that it would be understood for the next 2,000 years? Simple – take a common object that almost everyone is familiar with. Why wouldn't it be the relevant standard today?

  17. Sarah Kaye says:

    Yitzi Lefkowitz – yes but Rabbi Slifkin wrote this several years ago – so I do feel there should have been some credit given to him.

  18. David I. Waxman While you and Avi may be right that measuring by k'zayis is still as relevant as it was +/-2000 years ago, I cannot accept your argument. The whole point of the article is that for many Jews for many years the olive was not a common object that everyone was familiar with, and that is why mistakes were made in shiurim. I'm not sure there is any way to ensure that you will be understood 2000 years from now, we are all human after all…

  19. Zeke Kornberg Of course, we're looking for the best solution available. That's why they chose the olive. Why wouldn't it be relevant today? I didn't understand the basis of your question.

  20. Yitz Rephaeli says:

    Rabbi Slifkin wrote a blog about Rav Bar-Hayim’s article and did not mention your concern. Evidently he disagrees with your “feelings”. You should study up about kevod talmide hachamim.

  21. Yitzchoq Simm says:

    1) Rav Bar-Hayim produced two explicit quotes from Ashkenazi Rishonim. In one quote, the Raavya states that he is unfamiliar with olives. But you, somehow, know better. You claim that Raavya and ALL Rishonim knew what an olive is. How do you know what ALL Rishonim did or did not know?
    2) You claim that the Rishonim were not sure what was meant by an average or egori olive, but most certainly knew what an olive looked like. Do you have a source to support your claim? I doubt it, because not one of the Rishonim writes this. Your claims are based on a childish and naïve view of reality.
    3) In the other quote brought by Rav Bar-Hayim, another Rishon states that he knew how many olives are equal in volume to an egg because he had seen olives in Eretz Yisroel. Why did he have to wait to get to Eretz Yisroel to know this?
    4) Rav Bar-Hayim does not suggest that “all Rishonim are retarded idiots”. He claims and proves that Rishonim in certain countries had no direct experience of olives, whereas Rishonim from other areas did.
    5) Rav Dov Lior of Kiryas Arba makes the same claim as Rav Bar-Hayim regarding Ashkenazi Rishonim: see http://www.youtube.com/watch?v=OB3VRHZF_V8&feature=youtu.be @ 17 mins. Does Rav Lior also suffer from a Napoleon complex?
    6) It is apparent that you have a personal issue with Rav Bar-Hayim and lack derech eretz. Shame on you.

  22. Moshe says:

    HaRav David Bar-Hayim has held the halakhic position of the k’zayit being precisely that, an olive size for many years, way before the essay by Rav Slifkin so it is ridiculous to make a claim that his thinking is not “original.”

  23. Micha Berger says:

    Halakhah is not "as real as it gets". There is a difference in kind between trying to describe reality, and between defining law. We have other cases where law was based on things we currently do not believe about reality. E.g. The notion that maggots found within meat are kosher because they are produced abiogenetically from the meat. Or that one may kill lice on Shabbos, because they too are not born through sexual reproduction. Or that one may violate Shabbos to save a baby born prematurely in the 7th month, but one born in the 8th month isn't going to survive anyway the gemara tells you not to violate Shabbos to save it.

    And there are numerous approaches to how to deal with those issues. Some reexplain the law using today's understanding. Perhaps because the difference between our sages' notion of reality and what's really there isn't halachically significant. Others, such as the Vilna Gaon and Rav Kook, allow the new scientific knowledge to cause new stringency, but not new leniency. But none allow dismissing established and accepted law. Simply because generations of widespread acceptance creates legal authority.

    Technical knowledge about the size of olives in the classical period similarly would have little impact on binding law. Undoing law requires proving it is illegal. Not simply that it is superfluous or without a meaningful cause. So, for someone for whom more than a minimum of matzah would be dangerous (ciliac or other gluten intolerance, diabetes), who would thereby be violating laws about preserving health, now have grounds for leniency rather than stretching their medical limits. Similarly when the error in olive size means overestimating how rapidly a sick person would eat on Yom Kippur, we may be forced to adjust the top limit. In those cases, the error leads to legal flaws.

    The Oral Law is just that oral. Drift was built into the system. We aren't preserving facts, we are working a legal process. The issue isn't empirical accuracy but legal authority.

  24. Abe Kohen says:

    While there is variation in the size of olives, there is still greater variation in the size of eggs. Micha, in NJ compare the size of a Small to a Jumbo, then compare the size of a Large in NJ vs in Israel. Who is to say what the size of medieval German or French eggs were compare to Mesopotamian eggs?

    A Happy Kosher Paysach (when did the segol become a tzayray?) to you and your family.

  25. Micha Berger says:

    Abe Kohen We have remains of olives found at Masada. So, eggs or no eggs, we know that all accepted opinions about the kezayis are bigger than they were historically.

    I'm arguing that all of this is interesting theory, but only of marginal import WRT law. Law based on misunderstanding the facts is still law — authority comes from acceptance. As long as the mistake about realia doesn't lead to a legal problem. This whole focus on halakhah as fact-finding misses what halakhah is.

    English needs a type system for its nouns, so that law and empirical datum wouldn't be mistakenly interchanged.

  26. Ira Tick says:

    But where are we undoing a law?

  27. Ira Tick says:

    The law is an olive.

  28. Micha Berger says:

    Ira Tick – The law is as defined by consensus. Even if that's no longer an olive. See Maimonides' intro, explaining how the Talmud became binding.

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