Bava Batra 86: Acquisition and Reneging on Sales: Pulling, Lifting, Measurements

In daf 84, we are introduced to a Mishna that teaches a number of specific guidelines regarding acquisition.  If one purchases merchandise from another, it must be pulled.  Measuring is permitted, but acquisition requires pulling.  If a person wishes to acquire an item in another way, s/he can go through a somewhat elaborate process that includes renting one's place.  Flax is acquired through carrying rather than pulling or measuring.  Flax can also be acquired by pulling it from the ground.

Today's daf is a continuation of the Gemara as the rabbis discuss the implication of this Mishna.  What happens if one is pulling donkey drivers or labourers who then pull with them the merchandise in question?  Does one acquire through these actions, or perhaps when the merchandise is unloaded?  But what if the merchandise is not unloaded after all?

The Gemara notes that in Masechet Kiddushin (26a), a Mishna teaches that guaranteed property, ie. land, is acquired through money, a bill, or possession.  Movable property is acquired through pulling. A number of rabbis clarified this: movable property that is typically moved by lifted is also acquired by lifting - but not by pulling.

The rabbis apply the arguments of previously explored questions: when a person steals a purse on Shabbat, s/he is liable for both transgressing a halacha of Shabbat (punishable by death) and for stealing, even though only the harsher penalty should be applied.  Why?  Because one steals first and only then transgresses Shabbat halacha by leaving the private domain.  The rabbis question other factors, like whether the thief might be pulling the purse with a rope - is the purse acquired by pulling?  

The rabbis remind us again that things that are typically pulled are acquired by pulling while things that are typically lifted are acquired by lifting.  But is this truly the case?  The rabbis argue this point using the examples of flax, which is bundled and its bundles are lifted, and large or small domesticated animals.  

Our Gemara ends with a conversation about agreed upon measurements.  People are permitted to renege on their agreements to buy or to sell if the measurements agreed upon before the transfer of merchandise are invalid or inaccurate.  The vessels used to measure amounts must display markings that are available for all to see.