In which two cases in our Mishnah do Rav and Shmuel disagree whether the sale is valid if he wrote a Shtar, or only if she accepted on himself to guarantee it (Acharayus)?
Dan, New York, NY, USA
They only disagree about one case. This is the case where the buyer bought it from the violent "Sikrikon" and then re-bought it from the real owner. The Mishnah states that this sale is invalid. However, Rav (end of 58a) maintains that if the owner wrote a Shtar for the buyer this proves that he really does want to sell the field with total consent, while Shmuel maintains that a Shtar is not sufficient (because the owner might still have been forced by the bandits to write the Shtar). According to Shmuel, only if the owner wrote Achrayus to the buyer is this sufficient proof that he voluntarily sold it to the buyer and the sale is valid.
Kol Tuv,
Dovid Bloom