Bava Batra 7: What We Cannot Compel, Paying for a Wall to Surround and Protect the City

The Gemara explores two cases to better understand whether one co-owner can compel the other to share the cost of rebuilding shared property.  Although a person living on the lower story of a sinking first floor building cannot compel the upstairs owner to move out while he fixes his portion of the home, he is permitted to do so if the upper floor sinks by ten handbreadths.  At that point, the second floor has fallen into the domain of the first floor and thus the first floor's owner may take charge of repairs.  Similarly, one brother cannot compel another to take down a wall that he has built within his domain, even if that wall causes damages to his property.  

In their debate, the rabbis return to the question of a vineyard and a field built beside each other.  As well, they consider the naming of property: if a "hall" is now in fact a "dark room" because the windows have been blocked by a neighbour's wall, is that reason enough to compel the neighbour to take down the wall?

A new Mishna teaches that one can compel all residents of  a courtyard to contribute to building a gatehouse (to manage pedestrians entering the courtyard)  and that one can compel all city residents to contribute to the cost of building a wall, double doors and a crossbar to surround the city.  Rabban Shimon ben Gamliel disagrees with both of these orders.  The Mishna asks a question regarding the second statement: how long must one have lived in the city to have to contribute to building the wall?  The answer is twelve months, other than those who buy property in the city.  Once one owns property, one is expected to contribute to the expense of the wall.

The Gemara begins by questioning whether or not a gatehouse should be built at all.  Didn't Eliyahu stop speaking with a person who built a gatehouse?  The rabbis consider whether the gatehouse appropriately keeps people from one's courtyard, whether it is built in our outside of the courtyard, and whether or not it requires a key.  If a courtyard is close to the public domain it may indeed require a gatehouse to keep people from peering inside.  In times when the 'evil eye' is understood as  frightening curse, it is reasonable that people would wish to block others from peering into their homes.

Rabbi Elazar asks his mentor Rabbi Yochanan if a city collection to build a wall is based on the number of residents or the value of each resident; on each home's distance from the wall.  Rabbi Yochanan answers "My son" to him when he states with certainty that the cost is based on each person's worth (we have learned that each person was assigned a valuation) and that those who live closer to the wall should pay more toward their protection.  He says, "You can fix nails in this". 

Our daf ends with an important caveat.  Sages were exempt from paying for the cost of a wall or other protective measures.  The rabbis quote verses that allude to G-d's protection of those who serve him through mitzvot.  We close the book on today's daf with Rabbi Yochanan and Reish Lakish arguing about which verses are most helpful in this proof.