Bava Kamma 70: Rabbinic Power of Attorney

A practice from Neharde'a - where writing a document of agency or power of attorney was not permitted. (With the discussion of what the issues were) Also, a new mishnah - about stealing and then slaughtering it, when does one need to pay the penalty of the 4 or 5? Including the return of "kim leih be-derabbah minei" - when one I'd only given the harsher punishment for two violations in one act.