Nedarim 4:8 - 5:1

ור"י אוסר – for since there isn’t there another who would be able to provide other than him, it is like a gift. But the Halakha is not according to Rabbi Yossi. But especially when he (i.e., the one who has taken a vow not to benefit from his fellow) has nothing to eat, that the Rabbis permit, but not with another person.

השותפין – that each one of them a house in the courtyard, and the courtyard that is in front of the houses, both of them are partners in it But at the time when the courtyard has the law of division/partition, and as such there will be four cubits in the courtyard to each and every house in front of the house, and there will remain from the courtyard another four cubits to this one (i.e., person) and four cubits to that one (i.e., person), in this everyone admits that both of them are forbidden to enter into the courtyard until they divide it, for since the law of division/partition is there. But Rabbi Eliezer and the Rabbis do not disagree other than regarding a courtyard that does not have the law of division, as the Rabbis state that each of them enters through his fellow’s [property], but Rabbi Eliezer ben Yaakov holds that there is a retrospective designation (i.e., the legal effect resulting from an action selection or designation or disposal of things previously undefined for their purpose/ברירה) and this one goes to his and that one goes to his.

ושניהם אסורים להעמיד שם רחים וכו' – But Rabbi Eliezer ben Yaakov admits in all of these that the partners prevent each other, for it does not belong to permit for the reason of the retrospective designation, for since it is within his hand/power to prevent him, and if he doesn’t prevent him,it is found that he provides him benefit.

ופופין את הנודר למכור את חלקו – for we are concerned that after he sees his fellow entering, he will forget and will also enter. But when both are prohibited [from entering] we don’t concern ourselves, and specifically when he took a vow on his own not to enjoy benefit from his fellow is when we force him to sell his portion but if his fellow made him take a vow that he will not benefit from him, he is the victim of an unavoidable accident, and we don’t force him to see for what can he possibly do? But if you stated such, each partner should make his friend take a vow that he will not benefit from him in order that we can force him to sell his portion.