Bava Batra 55: The Effects of Boundaries on Chazaka, Pe'a, and Shabbat

In their discussions about different ways that different people might be permitted to acquire property from another, we first learn about the use of a hoe.  Can a person acquire an entire field based on striking the land just one time with a hoe?  This is discussed the case of a Gentile's land that is bought by a Jew and then is possessed by a second Jew.  The second Jew does not lose possession of the land.

The rabbis then consider Persian law, which allows possession of another's land based on chazaka only after forty years of possession.  The implications of this practice on tax law and inheritance is considered.   Inheritance changes based on the behaviour and actions of fathers and sons.  

The Gemara notes that boundaries are created for different purposes and can serve different functioning.  A barrier created to demarcate the barrier between a field belonging to a convert without heirs and another field or a sea squill (a specific tree with a large round root ball that dries out in the summer) does not block access to pe'a.  Pe'a refers to the corners of fields left unharvested to serve the needs of the poor and strangers.  Pe'a must be given separately if a field is crossed by:

• a stream
• a canal
• a public road more than 16 cubits wide
• a private road more than 4 cubits wide
• a public trail
• a permanent private trail (one that is used in all seasons)

The Gemara asks to compare these with the demarcations of boundaries that inform the transmission of tuma, ritual impurity.  As taught in Teruma, the rabbis note that they disagree about whether or not ritual impurity is transferred outside of a private domain.  

Regarding Shabbat, the halachot might be different.  It is argued that boundaries do not create barriers between fields concerning the halachot of Shabbat, including eiruvin.  Eiruvin are the boundaries within which one is permitted to carry and do perform other specific actions that are restricted on Shabbat.  It is also argued that one might carry a half of a fig back and forth across a boundary on Shabbat, for example, without noticing what one has done.  In this case, one might be exempt.