As we learned previously, someone who cannot derive benefit from another person because of a neder, cannot profit from anything that belongs to him, even if he is not the sole owner of the object. The fifth chapter of Massekhet Nedarim which begins on our daf deals with a list of situations where the forbidden property is owned only in part by the person whose possessions are forbidden. Thus the discussion revolves around what circumstances make a person considered to be the owner of an object (at least in part). A related question is how public property should be treated. Do we consider public property to be owned in partnership by all members of the community?
The first Mishna in the new perek discusses a case where two people who were equal partners in the courtyard of a house took vows forbidding each other from benefiting from one-another. In such a case, the Tanna Kamma forbids each of them to enter the courtyard, since all of it is partially owned by the other person, from whom he cannot derive any benefit. Rabbi Eliezer ben Ya’akov permits each of them to enter the courtyard – each to the portion that he has designated for his own use. All are in agreement, however, that one of them cannot set up a mill or an oven or raise chickens in the courtyard.
Several explanations are put forward regarding the last halakha – that one of them cannot set up a mill or an oven or raise chickens in the courtyard. One suggestion made by Tosafot and the Ran is that even though ordinarily partners allow each other to do these things, since they require permission it would be considered vitur – a concession – which cannot be made in this case. Tosafot also point out that in the case of a mill we can assume that the owner will bring customers in who will inevitably make use of the partner’s side of the courtyard, which will be forbidden. Similarly, chickens will certainly wander around the entire courtyard, eating whatever they find, even if it belongs to the partner.