Duchsustus

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Duchsustus is one of three Talmudic names for animal skin. The other two are klaf and gvil. The meanings of these terms, however, are the subject of Halachic controversy. The Talmud tells us that ideally a sefer Torah should be written on gvil, Tefillin should be written on Klaf and Mezuzah should be written on duchsustus. This is a halachah that dates back to Moshe at Mount Sinai.

Duchsustus is a name for a type of parchment used for religious writings in Judaism. It is originally a greek word. The upper layer of the animal skin is called klaf. The lower layer of the skin is called duchsustus25. The entire skin (both layers) when processed together and not separated is called gvil. The Talmud26 tells us that ideally a sefer Torah should be written on gvil, Tefillin should be written on klaf and Mezuzah should be written on duchsustus. This is a halachah that dates back to Moshe at Mount Sinai. These definitions and rulings are the halachic conclusions of Rabbeinu Tam and the Shulchan Aruch. As mentioned before, however, the issue is a matter of great controversy. The Bais Yoseph himself has dealt with the subject matter. What follows is therefore the Bais Yoseph's own words (OC 32:7): The commentaries disagree as to the meaning of Klaf and Duchsustus. The RaN's View

The RaN27, citing the Rambam, writes that when the skin is being processed it is split into two. The section that is stuck to the flesh is called "klaf" and the writing is done on the side that is facing the flesh itself. The section that is toward the hair is called "duchsustus" and the writing is done on the side that is facing the hair. He (the RaN) further writes that this is the opinion of the Ramban and the Rashba in a responsa28. The Ran also writes that according to this opinion, those that write Tefillin must meticulously scrape off the skins toward the side of the hair so that what will remain will be considered within the category of Klaf. The View of Tosfos

However, the Tosfos29 have written the exact opposite. The upper section that is toward the hair is called "Klaf", while the inner section that is attached to the flesh is called "duchsustus." According to this, when we say that it is written "on the Klaf facing the flesh" - it means the side that is closer to the flesh. When we say "on the duchsustus facing the hair" - it means on the side that is closer to the hair. It comes out that regarding both of them we write on the side where the two connect together. The Mordechai, citing Rashi30, also ruled in this manner; as did the Ran31 citing the Aruch, the Rosh Hilchos Sefer Torah Siman 5; our versions of the Rambam (1:7); Sefer HaTrumah Siman 194; SmaG Siman 24, and HaGaos Maimon 1:4. The Tosfos have also commented on this (Shabbos 79b "Klaf"): "And our parchments have the status of klaf and we write on the side that faces the flesh, not like those who say that our parchment is duchsustus, because the craftsmen who process it scrape off the outer layer and what remains is the duchsustus. For if so, how could we write Tefillin on them? For we conclude here that Tefillin must be written specifically on Klaf." All the Rabbis that cite Tosfos have ruled in the same manner. The rationale must be that the upper layer toward the hair that is scraped off is only what is needed to process and smooth it. Even if the skin is into two - it would be necessary to scrape it off in such a manner. And on the side of the flesh they scrape off so much that only the Klaf remains." [Up until here is the translation of the Bais Yoseph]. There are a number of responsa of the Rambam that also indicate that the Rambam's position is, in fact, as the RaN describes32. Nonetheless, the Halachah is in accordance with the Shulchan Aruch and Rabbeinu Tam's position - the duchsustus is the bottom part of the skin, and the writing is done on the inner sides. Special Mitzvah to Use Duchsustus

It is a special Mitzvah to write the Mezuzah on duchsustus. Indeed, the Tur writes that the essential Mitzvah of Mezuzah is to write it on duchsustus33. If it was written on klaf or gvil, the Mezuzah is still kosher34. For a discussion on why duchsustus is not made today see footnote35. The writing is always done on the middle of both layers of skin. When klaf is used the writing is done on the side toward the flesh. When duchsustus is used the writing is done on the side closest to the outer skin36. Nowadays, however, the animal hide is no longer split into klaf and duchsustus. Rather, the entire skin is processed and smoothed on both sides and the writing is done on the side of the animal's flesh37. If a Mezuzah is written on the other side, i.e. on the side of the hair, the Mezuzah is invalid according to most authorities38.