Nedarim, Chapter Five, Mishnah One
In the time of the Mishnah, peoples homes opened into jointly possessed courtyards. The custom was to use the courtyard for various purposes, including cooking, grinding wheat and raising chickens. However, each resident could prevent the others from using the courtyard for such purposes.
Our mishnah discusses a situation in which either both or one of the owners of the courtyard has taken a vow not to benefit from the other. The question is, can they still use the courtyard?
1) If joint owners [of a courtyard] made a vow not to benefit from one another, they may not enter the courtyard.
a) Rabbi Eliezer ben Jacob says: This one enters his own property and this one enters his own property.
2) And both are forbidden to set up a mill-stone or an oven or raise chickens.
3) If [only] one was forbidden by vow to benefit from the other, he may not enter the court.
a) Rabbi Eliezer ben Jacob says: He can say to the other, I am entering into my own, and I am not entering into yours.
4) They force the one who vowed to sell his share [of the courtyard].
Section one: If both owners of the courtyard vowed not to benefit from the other, according to the first opinion neither may enter the courtyard at all. As we learned above (4:1), one who is not allowed by vow to benefit from another, may not walk on his property. Since the property is jointly owned, each one would be entering the others property.
Rabbi Eliezer ben Jacob holds that since in general both people can enter the courtyard, neither is really entering someone elses property. At each point where he stands he could claim that this part is his. Therefore, both can enter the courtyard.
Section two: Neither may use the courtyard for any of its normal uses. Rabbi Eliezer ben Jacob would agree with this, since putting any of these things in the courtyard requires the neighbors permission, and in this case, permission cannot be granted.
Section three: If only one owner is prohibited by vow from benefiting from the other, he may not enter the courtyard. Again, Rabbi Eliezer ben Jacob holds that this is permitted.
Section four: In such a case, the one who vowed must sell his share of the courtyard, lest he come to use the courtyard, which even Rabbi Eliezer ben Jacob prohibits. However, this is only true if he himself swore not to benefit from his neighbor. If his neighbor swore that he should not benefit from him, he is not forced to sell his share of the courtyard.