Sunday, March 14, 2021

Monsters and Matzos

Here's a terrific riddle for Rosh Chodesh Nissan!

On Rosh Chodesh, we recite Barchi Nafshi, which mentions leviathan - the whale. What is the connection between the relatively rare findings of ancient whale bones on the coast of Israel, and the large size of matza that many people eat on Seder night?

And the answer is...


(giving you time to guess)

... follows:

In areas such as north-western Europe, there was a large whaling industry. That's because they needed whale oil for lamps. But in Israel and the surrounding regions, they lit lamps from olive oil, and so there was never much of a demand for whaling. On other hand, because they didn't have olives in north-western Europe, not only did they need to hunt whales, but they also didn't know how big a kezayis was, and thus ended up with a large shiur of matzah!

What a great riddle for Seder night!

With Pesach approaching, it's kezayis season again. The monograph that I wrote on the evolution of the kezayis, from the size of an olive to a matzah ten times that size, seems to be the most popular piece that I have ever published. If you haven't read it, you can download it at this link. And it's also in my new book Rationalism vs. Mysticism, which you can purchase at this link.

Here is a list of other posts relating to this topic:

Matzah/Maror Chart for Rationalists - so that you, too, can have a chart!

The Popularity of Olives - exploring why this paper is so popular and yet hated by some.

Why On Earth Would One Eat A Kezayis?  - discussing the strange notion that one should aim to eat a kezayis of matzah on Seder night.

The Riddle of the Giant Kezayis Defense - wondering why many people would not accept that a kezayis is the size of an olive.

Maniacal Dishonesty About Olives - exposing an error-ridden critique that appeared in the charedi polemical journal Dialogue.

It's Krazy Kezayis Time! - discussing the view that one should eat a huge amount of matzah in a very short time in order to fulfill all opinions.

The Kezayis Revolution - announcing the fabulous sefer by Rabbi Hadar Margolin, which presents the same arguments that I brought but in a more yeshivish manner. He also brings an astonishing array of evidence that many recent charedi gedolim likewise held that a kezayis is very small, including even the Chazon Ish! Best of all, the entire sefer can be freely downloaded.

Meanwhile, the new Biblical Museum of Natural History is open for tours, and will be open over Pesach too. However, unless the Covid restrictions are further relaxes, we are extremely limited in how many people we can accommodate. So book your tour now! Visit for more details.


  1. Rabbi - can I please suggest you get an SSL certificate for this site?

    1. I have no idea what that means or how to do it.

    2. He's saying that you site is insecure.


      Your SEO will be improved so that more of the masses can be treated to screeds about how middle class mores are so superior to those of poor people.

    4. It says "Save Failed. You have not been authorized to use this domain. Please follow the settings instructions."

  2. Rabbi Slifkin, you wrote in your monograph that there is no talmudic source for saying that the size of a kezayit shrunk. What about the gemara in Sotah that talks about the huge size of the grapes carried by the spies? Wouldn't that indicate that the size of fruits has shrunk?

    1. First of all, that's not between Chazal's time and our time - it's between Biblical times and Chazal's time.
      Second, the Gemara says nothing about the huge size of grapes. It's talking about the huge size of the CLUSTER.

    2. I hear what you're saying, but I don't understand why it would matter if it's between biblical times and chazal's time vs chazal's time and our time. At the end of the day, it would mean that fruits got smaller at some point according to Jewish tradition- maybe just like chazal believed fruits got smaller since biblical times, it follows for us to believe they followed the same trend to our times.
      Although good point with the cluster, I didn't think of that.

    3. But we *know* that they didn't get smaller since the time of Chazal. And of course Chazal wouldn't have thought that, because they lived back then.

      It's also pretty clear that descriptions of the fruit of the meraglim are meant to be supernatural, and of course that is all aggadata in any event.

    4. Question on the cluster detail - there are portrayals of that scene from the meraglim showing 8 spies carrying the cluster, and two other spies each carrying a single fruit (pomegranate and fig or something) - but each of these other fruits was humungous, thus necessitating the single fruit-to-person ratio. (And Yehoshua and Kalev carried nothing as they knew that these fruits were going to be used as part of the "Everything is SO BIG... EVEN THE PEOPLE" argument). So it is that the fruit itself was large, not just the bunch.

      And I think that this image is based on the midrash, not some 20th century children's book author. But I do not know the actual source.

      (That doesn't entirely undermine the argument that that was Biblical to Chazal's time; Josef's argument of "in hachi nami" probably also still has merit...)

    5. @Josef the problem with your argument is that we have 1st century (Tannaitic period) seeds from archaeological digs in Israel and the fruit produced upon planting them is either the same size as modern fruits or smaller. Even if we took the gemara in Sotah at face value that fruit was at one time bigger, 1st century fruit was not as evidenced both by planting seeds from archaeological digs as well as from portrayals of fruit in period artwork.

    6. @Yosef R, if the size of that fruit (or the cluster) were “normal” by the standards of the time, why does the Torah go out of its way to note it? It seems more reasonable to say the Torah mentioned that specific cluster (and even named the Wadi after it) because of its very unusual properties. If all the fruit (or clusters) of the time were similar in size (and other properties) to that one, why would spies have even carried it back to the Israelite camp? How could the spies have relied on the size of that cluster as evidence of the size of the people if there was not something very unusual about that particular cluster? Seems to me that cluster might have been able to win a blue ribbon prize at a state fair in Nebraska or something. But it was probably not representative of anything in general during that age.


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