The Talmud cited the following incident: There was once a food shortage in Nehardea. All the people sold their mansions. Eventually, wheat arrived and Rav Nachman told them that the law is that the mansions must be returned to their original owners.

The Talmud notes that the reason why sales are void is because they were made in error, since it became known that the ship carrying the wheat was waiting in the port at the time the mansions were sold.