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.
The Talmud in the daf yomi adds that this would explain the following conversation: Rami bar Shmuel said to Rav Nachman, if you rule like this, you will cause them trouble in the future. Rav Nachman replied that a food shortage is not common, and therefore we need not worry about the next one. Rami bar Shmuel retorted that a food shortage in Nehardea is indeed a common occurrence!
There are many legal issues that this Talmud is used to resolve.
Reuben desperately needed an operation and he desired a certain expert doctor to perform the surgery. The hospital told him that he presently was outside of the country, and will only be returning the following week. Reuben vowed an enormous amount of money to charity if the surgeon would return earlier than he originally intended. As soon as he uttered those words, the doctor was standing by his bedside. He told Reuben that he had decided to shorten his vacation. The question was asked – was Reuben obligated to fulfill his vow? Perhaps, he was not required to give the money to charity, for at the time that he pronounced the vow, the doctor was already in the country.
There was a certain city where a terrible edict was issued against the residents. They sent a message to a well-known Rabbi, who was famous for delivering miracles through his prayer. The Tzadik agreed, but requested of them to send a certain amount of money that he would be able to distribute to the widows and orphans residing in his city. A short amount of time after they sent the money, they received a letter that the decree had been cancelled. The city was overjoyed. However, one resident sent a letter to the Maharsham saying that perhaps, they should get their money back because he noticed that the date on the letter stating that the decree had been cancelled was before they actually sent the money. It appears that the giving of the money was erroneous.
Reuben and Simon bought two lottery tickets together. They made up that they each would share the winnings of each ticket. The reason for this decision was based on the Talmud in Bava Metzia that states that the mazal of two people together is better than one. After the lottery numbers were chosen, Reuben went to Shimon attempting to switch the deal. He said, let us each keep the winnings of our own individual ticket. Reuben did this because he already knew that the ticket that he was holding was chosen and he would receive fifty thousand dollars. Simon agreed to this new deal. The reason that Simon agreed was because the ticket that he was holding was chosen, and he would now receive the full share of a two hundred million dollars. Can Reuben now retract from the second deal?
Based on the decision of the Talmud, in all three cases it would seem, the money does not transfer when a deal was made after the circumstances causing deal are no longer prevalent.