The rules and regulations of eiruvin that have been discussed throughout this tractate, are but one aspect of a much larger set of halakhot, that are referred to as shvut – Rabbinic ordinances whose purpose is to keep the individual from committing a more serious transgression or to guarantee an atmosphere of Shabbaton – of rest and tranquility – on Shabbat.
The final chapter of Massekhet Eiruvin, which begins on our daf , moves away from a discussion of eiruvin and deals with broader issues of such Rabbinic ordinances, although most of the issues discussed are in some way connected with carrying on Shabbat.
The first Mishna in this perek discusses someone who finds tefillin in a public domain on Shabbat and is interested in protecting them by bringing them into a protected area. How can they be carried on Shabbat? The agreed solution of the Mishna is that transporting them by wearing them is permitted. The Tanna Kamma (first) and Rabban Gamliel disagree as to whether only one pair can be worn at a time, or, perhaps, even two pairs can be worn.
The Gemara suggests a number of reasons for the difference of opinion between Rabban Gamliel and the Tanna Kamma. One suggestion is that they differ on whether the commandment of tefillin applies on Shabbat or not. According to the Tanna Kamma, the mitzva does apply, so wearing two pairs of tefillin simultaneously would be forbidden because of bal tosif – the commandment that forbids adding to a mitzva. According to Rabban Gamliel, who does not believe that the mitzva of tefillin applies on Shabbat, there is no concern that you are adding to the mitzva by wearing two pairs.
It should be noted that according to the conclusion of the Gemara, tefillin should not be worn on Shabbat. Nevertheless, in our case, where we are concerned lest the holiness of the tefillin will be desecrated if they are left in the public domain, there is general agreement that we permit them to be worn for the purpose of moving them to a safer place.