QUESTION: The Gemara says that Tefilin may not be written on the hide of a Tamei animal, because the flesh of that animal is not "Mutar b'Ficha" (permitted to be eaten), as derived from Shemos 13:9).
The SEFER HA'MANHIG asks that this verse was spoken by Hash-m to the Jewish people before the Torah was given at Har Sinai. How, then, can the verse teach that Tefilin may not be written on the hide of a Tamei animal which may not be eaten, when, at the time that this verse was said, it was permitted to eat Tamei animals?
(a) It is true that the Torah does not mean that the Jewish people were given the Mitzvah of Tefilin at the time they left Egypt, before they received the Torah. Only when they received the Torah did they receive the Mitzvah of Tefilin, at which time they also were told which animals are forbidden. It is also possible that the Mitzvah of Tefilin became obligatory only from the time that the Jewish people entered Eretz Yisrael.
The Sefer ha'Manhig proves this from the fact that Tefilin contain four chapters from the Torah, and two of those chapters were not spoken to the Jewish people in Egypt, but only at Har Sinai. It must be that the Mitzvah of Tefilin was not given until the Torah was given at Har Sinai, or until the Jews entered Eretz Yisrael. By that time, the Tamei animals were already forbidden.
(b) Other Rishonim maintain that the Mitzvah of Tefilin applied even from the time that the Jews went out of Egypt (see, for example, CHIDUSHEI HA'RASHBA to Menachos 35b). According to these Rishonim, what is the answer to the Sefer ha'Manhig's question? It must be that there was a tradition that the Jewish people had received from their forebears that certain animals were destined to be forbidden when the Torah would be given.


OPINIONS: The Gemara discusses the prohibition against dipping food in salt water on Shabbos. Why is such an act prohibited?
(a) RASHI (DH v'ha'Lo Hu, DH Ein Molchin) writes that when one salts food, one is Mesaken ("fixes") the food. Rashi seems to compare salting food to completing a utensil, which is forbidden because of Makeh b'Patish.
(b) The RAMBAM (Hilchos Shabbos 22:10) writes that it is forbidden because of Bishul, since salting "cooks" the food in a certain respect.
(c) TOSFOS earlier (75b, DH Ein Ibud) implies that salting food is forbidden because of Mole'ach u'Me'abed (processing hides). Even though the Melachah of Me'abed does not apply to food items, that is only mid'Oraisa. Mid'Rabanan, though, it is forbidden to process foods.
Rashi, at the end of his comments to the Mishnah here (end of DH v'Elu Hen), also implies that there is an element of Me'abed involved when one salts food.