While the third chapter of Massekhet Eiruvin dealt with the person who has an established place to spend Shabbat, but desires to change or extend the boundaries of that place, the fourth chapter introduces us to the individual who does not have a place for Shabbat. For example, such a person may be “on the road” when Shabbat begins, or, perhaps leaves his city and travels more than 2,000 amot beyond its boundaries. The first Mishna (41b) teaches that someone who leaves the precincts of the city – even if he is forced to do so by non-Jews or a ru’ah ra’ah – an “evil wind” (the term can variously refer to temporary insanity or to an actual wind that creates a storm that drives the individual beyond the tehum (=limits). Maimonides, in his commentary on the Mishna, argues that any event beyond one’s control can be referred to as a ru’ah ra’ah) – loses his ability to travel and is limited to the four cubit area in which he is standing.
Recognizing the difficulties involved in restricting someone in that fashion, the Gemara records the question that was presented to Rabba.
They raised a dilemma before Rabba: If a person who is restricted to an area of four cubits needed to relieve himself and no secluded spot is available, what is the? He said to them: The Sages established a principle that great is human dignity, which even supersedes a negative precept of the Torah, and therefore a person is permitted to overstep the limit fixed by the Sages in order to relieve himself modestly.
The Sages of Neharde’a add that once he has returned to the city in a permissible manner, he now can walk freely within the city.
The source for Rabba’s ruling is the Gemara’s understanding of the passage regarding returning lost objects ( 22:1) that is interpreted to mean that if returning the object will involve embarrassment to the finder, he is allowed to ignore the lost object and pass up the opportunity to return it (see Bava Metzia 30a). The conclusion there is that generally speaking K’vod HaBeriyot can “push aside” all Rabbinic laws, of which eiruvei tehumim is an example.
The rishonim debate whether the concept of K’vod HaBeriyot is defined by the person’s own, personal dignity, and it would be impossible to remain in the same four cubits after having relieved himself there (the position taken by Rabbenu Hananel and Rabbennu Yehonatan) or if the concept is defined by one’s relationship with others. According to the Rosh, who bases his position on Rav Hai Gaon, K’vod HaBeriyot applies only if there are other people in the vicinity whose presence embarrasses him or who will be offended were the individual to relieve himself in front of them.