On this daf, we find a question about selling one’s inheritance.
There was a man who lost his horse. He hoped that it would return, but after eight days, he was reasonably sure that it was lost forever. When a friend asked him to sell the rights to the lost horse to him, he was surprised. “It may never come home and you want to pay money for it?”
The man quickly explained himself. “Well, it was an exceptional horse and it may come home. And I would not pay much for the rights to it on the off-chance it comes back…”
The merchant decided to take the money and forgot about the entire matter.
To his surprise, his horse returned about a week later. When the buyer came to take the animal, the seller refused to give it to him. “You can take the money back, but not the horse. I only sold it to you because I didn’t believe it would return. Now that it is here, I cannot part with it, so I changed my mind.”
The buyer claimed that he could not go back on the sale, however. “A deal is a deal, no matter what, as I am sure you will find out when we speak to a rov.”
When this case was presented to Rav Menachem Mendel, the av beis din of Sighet, he ruled: “The seller is correct that he can change his mind. What kind of kinyan can be made on something that was lost to everyone, possibly forever? It is not binding on the seller” (Divrei Hageonim).