As we learned on yesterday’s daf, when a child must be circumcised on Shabbat, the Shabbat prohibitions can be overridden by the mitzva to perform the berit mila. On today’s daf we learn that Rabbi Eliezer believes that this is not a halakha that is unique to circumcision; in fact there are many commandments that override the laws of Shabbat. For example, the Gemara teaches that such mitzvot as lulav, sukka, matza and shofar will all take precedence over Shabbat, if necessary. Rabbi Yohanan teaches, however, that –
Rabbi Eliezer did not say with regard to all mitzvot that actions that facilitate performance of a mitzva override Shabbat.
This is not a fixed principle with regard to preparations for all mitzvot. Rather, each case must be considered on its own merits, and proof must be cited that this principle applies to a specific mitzva.
Which mitzvot do not override Shabbat even according to Rabbi Eliezer?
Rav Adda bar Ahava said: The statement of Rabbi Yohanan comes to exclude attaching ritual fringes to his garment and affixing a mezuza to the doorway, which do not override Shabbat. The Gemara notes that that was also taught in a baraita: And they, Rabbi Eliezer and the Rabbis, agree that if one attached ritual fringes to his garment on Shabbat, and similarly, if one affixed a mezuza to his doorway on Shabbat, that he is liable.
The Gemara explains this as follows:
Rav Nahman said that Rav Yitzhak said, and some say that he said that Rav Huna, son of Rav Yehoshua, said: The actions that facilitate the performance of these mitzvot do not override Shabbat, since one can render the relevant objects ownerless.
One is only required to perform these mitzvot if the objects, i.e., the garment and the house, belong to him. If he renders them ownerless, he is no longer obligated to perform these mitzvot.
According to Rashi, who is of the opinion that there is an obligation to affix ritual fringes even to a garment not currently in use, rendering one’s garment ownerless is the only way to exempt oneself from the mitzva to affix ritual fringes to its corners. According to other authorities, who rule that a garment which is not being worn is exempt from ritual fringes, either the Gemara chose one rationale from a number of possible explanations (Rashba), or this reason was chosen because it applies to both ritual fringes and mezuza (Ramban).