A principal hiding in plain sight TB Shabbat 79

Today’s daf TB Shabbat 79 discusses the stages of tanning a hide.  “Rabbi Ḥiyya bar Ami said in the name of Ulla: There are three hides, i.e., three stages in the process of tanning hides, and at each stage it is known by a different name: Matza, and ḥifa, and diftera. Matza, as per its plain meaning, with no additives… Ḥifa is hide that is salted, and not treated with flour, and not treated with gallnuts… As we learned in the mishna: The measure that determines liability for carrying out animal hide is equivalent to that which is used to make an amulet… Diftera is hide that is salted, and treated with flour, and not treated with gallnuts. And how much is the measure that determines liability for carrying out that hide on Shabbat? The measure that determines liability for carrying it out is equivalent to the amount which is used to write a bill of divorce on it” (Sefaria.org translation)

Diftera can be separated into two parts parchment (klaf קלף) and dokhsostos. When writing on parchment, one writes on the side of the hide that faced the flesh; on dokhsostos, one writes on the side of the hide on which there was hair.

All this serves as the introduction to a very important principle. Ma’alin bakodesh velo moridin

(מעלין בקדש ולא מורידין), one may upgrade to a level of greater sanctity, but not downgrade from a level of greater sanctity. The case in today’s daf deals with the different levels of sanctity of a mezuzah, tefillin, and a Torah scroll. “Similarly, tefillin that became tattered and a Torah scroll that became tattered, one may not make them into a mezuza, despite the fact that identical Torah portions appear in all three. This is prohibited because one does not downgrade from a level of greater sanctity, i.e., a Torah scroll or tefillin, to a level of lesser sanctity, i.e., a mezuza.” (Sefaria.org translation)

This principle also decides the appropriate observance of Hanukkah. There is a disagreement between Bet Shammai and Bet Hillel concerning the lighting of the Hanukkah candles. Bet Shammai says you begin with eight candles the first night and each following night you remove one candle. Bet Hillel teaches you begin with one candle and add a candle each night because Ma’alin bakodesh (מעלין בקדש), one may upgrade to a level of greater sanctity. (TB Shabbat 21b) And that is the correct practice to this very day.