2,780. Two Who Are Prohibited to Benefit From One Another

Hilchos Nedarim 7:1

If two people are prohibited by a vow or an oath to benefit from one another, they may return lost objects to one another because that’s a mitzvah. In a place where the practice is to reward one who returns a lost object, the reward should be given to the Temple treasury. This is because if person A accepts the reward, he’s receiving benefit from person B; if he doesn’t accept it, person B will be benefitting from him.

Hilchos Nedarim 7:2

Person A and person B are both permitted to use things that are communally owned by the Jewish people, such as the Temple mount, its chambers, and a well in the public thoroughfare. They may not, however, use things that are communally owned by the residents of their city, such as their town square, bathhouse, shul, aron and sefarim.