MISHNA: Partners who vowed not to derive benefit from one another are prohibited from entering into a courtyard that they jointly own, since each one has a portion in it and benefits from the share owned by the other, thereby leading to a violation of the vow. Rabbi Eliezer ben Ya’akov says: It is permitted for both to use the courtyard, as it can be said that since each has a portion in the courtyard; this one enters into his own portion and that one enters into his own portion.