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I am studying medieval Passovers.  In the course of my research I came across the passage in b. Talmud Pesachim 46a where it discusses deaf dough, describing it as having been mixed longer than it takes a man to walk from the Fish Tower to Tiberias.  I find this an unusual measurement—not everyone can be expected to have visited Tiberias and learned how far that is.

How was a normal Jewish household supposed to know if their matzah had been mixed and baked in the stipulated time, making it all right to eat during Passover?  Clocks did not have minute hands until the late 1600s, and bells on churches did not ring every 15 minutes.  Some English translations of the passage render the phrase as “18-24 minutes.”  How do they know that’s how long it took to make that walk?  I know 18 is chai, but that doesn’t account for the 24.

In medieval recipes from Christian households, you can find instructions to cook something for as long as it takes to say a certain prayer.  That seems like an unlikely solution to keeping track of a short period of time in a Jewish home because saying a prayer only to measure time might violate the commandment not to take G-d’s name in vain.

Somewhere there must be a discussion of this topic (hopefully translated into English).  Where should I be looking?  Any help would be appreciated.

Dear Katie,

Thanks for writing. I had a chance to learn the origin of a translation, and I am grateful. I'm also a teacher of cooking/baking and it was a fun subject.

First of all, consider using a reliable translation and commentary if you are looking in English. One of the best is still Adin Steinsaltz's translation.

I checked it out and it follows with the URL. The rest is up to you. :-)

It would appear that experienced bakers of matzah could knead the dough, "thump" it for the sound that it makes and/or compare it to other dough. The Gemara also describes a practical way of timing, = the time it takes to knead, shape and bake to completion.

Moreover, there were time-telling water-clocks in the Roman period if not earlier. It could easily be constructed, as could a sun dial.

Good luck.

Rabbi Dov
Pesahim 46a-b - Deaf dough   August 05, 2013

Today the custom is to make sure that the entire process of baking matza takes less than 18 minutes from beginning to end. As we will see, this ruling stems from a discussion in the Gemara on our daf (page). Nevertheless, in the time of the Mishnah, dough was usually considered hametz when it showed certain signs of leavening (see daf 48).

Mishna: Deaf dough [batzek ha-heresh ] is dough for which it is difficult to determine if it has been leavened. It is comparable to a deaf-mute, who cannot communicate. If there is dough similar to it in that water was added to both at the same time, which became leavened, the deaf dough is prohibited.  Although it has not shown external signs of becoming leavened, it can be presumed that the deaf dough has also become leavened.

Rashi explains the expression batzek ha-heresh as dough that does not clearly indicate whether it has become hametz and is difficult to understand, like a deaf person who has ears, yet we cannot tell whether or not he can hear.

According to the Rambam, dough that has become hametz makes a certain noise when you drum on it. The case in the Mishnah is one when no such noise is heard, so it is "mute." [deaf=deaf-mute BDL]

The Ramban explains that just as a deaf person has trouble hearing, similarly this dough is having trouble rising.

According to the Ge'onim the expression stems from the perception of people at that time that a deaf person could not be educated and was considered "retarded." This dough that did not follow the normal development pattern was compared to that situation.

The Gemara's question is: What should be done if no other dough was made at the same time so that there is nothing to compare it to?

Rabbi Abahu quotes Resh Lakish as saying that the amount of time that it takes to become hametz is the length of time that it takes to walk a mil – the distance from Tiberias to Migdal Nunia.

The opinions on the definition of this amount of time range from 18-24 minutes.  Given the severity of the prohibition of hametz the usual practice, as mentioned above, is to arrange for baking to be completed within 18 minutes.
This essay is based upon the insights and chidushim of Rabbi Steinsaltz, as published in the English version of the Koren Talmud Bavli with Commentary by Rabbi Adin Steinsaltz, and edited and adapted by Rabbi Shalom Berger. To learn more about the Steinsaltz Daf Yomi initiative, click here.  

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Rabbi Barry Dov Lerner


Write to me with questions about Jewish customs and law, history, philosophy and tradition for answers from a Conservative perspective or conversion. I am a graduate of The Jewish Theological Seminary and a member of the Conservative Rabbinical Assembly. Having served in congregational pulpits since 1970, I now am President of the Foundation For Family Education, Inc. a non-profit educational endeavor. I established it to create new formats of hands-on programs and provide free educational downloads at In addition to general informational questions I welcome your questions about programs for social action, outreach to dual-faith families, inter-faith clergy projects, healing services, education for conversion, adult education for the congregation and the community. If you have questions about Informal and Formal Education I am ready to share my extensive experience with Youth Activities, Camping and Religious School/Hebrew High School on a congregational, community and national/international level.


I have served on the National Youth Commission for more than 25 years and serve on the Boards of the Conservative Zionist movement MERCAZ and the World Council of Synagogues. I have always dual-families and taught candidates for conversion with a great sense of fulfillment. I am very proud of 25 years on the Jewish camping staff of Camps Ramah. My greatest source of pride is my family! Ask me about them, please!:-)

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