Excitement was in the air as the twelfth Siyum Hashas of the Daf Yomi cycle approached. Mendy, who had joined the Daf seven and a half years earlier, eagerly anticipated taking part in the major event at MetLife Stadium, along with 90,000 other participants.

Ten days before the Siyum, Mendy was blessed with a baby boy. He didn’t expect that this would affect his attendance at the Siyum, but the baby was yellow and the bris had to be delayed for a few days.

The night before the Siyum, the mohel checked the baby and informed Mendy that the bris could probably take place the following afternoon.

In the morning, at the Daf group, Mendy told his neighbor Ezra, “I bought a $180 ticket to the Siyum tonight, but will not be able to make it. Do you know of anyone who is still looking for a ticket?”

“Rabbi Kurz is looking for an extra ticket,” said Ezra. “He might be happy to buy it from you.”

“If you can sell it for me, I would very much appreciate it,” said Mendy, “It cost $180, but I’ll sell it for $150, or even $120.”

Ezra called Rabbi Kurz. “Someone in our Daf group has a $180 ticket to the Siyum that he won’t be able to use,” he said. “Are you interested?”

“Absolutely!” exclaimed Rabbi Kurz. “If you can bring me the ticket, I’ll pay the $180 immediately.”

Ezra decided not to mention that Mendy had only asked for $150. He put aside $150 for Mendy and kept $30 for himself.

“All’s well that ends well,” thought Ezra with satisfaction. “Rabbi Kurz got his ticket to the Siyum, Mendy recouped the $150 he wanted, and I earned thirty dollars in the process!”

While driving to the Siyum, Ezra told his chavrusa, who learned regularly in a business halacha shiur, what had happened with the ticket.

“You had no right to charge Rabbi Kurz the extra $30,” said his chavrusa. “I think you should return it to him.”

A lively discussion erupted in the car.

“Since you sold the ticket for Mendy, whatever you got for it is his!” said another person. “You have to give him the full $180.”

“I don’t see any problem in what you did,” a third passenger said. “Mendy got his price, and the rest was given to you. You earned it!”

“You and Mendy should split the $30,” a fourth person suggested, “since you both had a share in it.”

They debated the issue for twenty minutes. Finally, Ezra said, “Why don’t we ask Rabbi Dayan at tomorrow’s Daf?”

The following morning, when the Daf shiur finished, Ezra related the story to Rabbi Dayan.

“What should I do with the extra $30?” he asked.

“This question was posed to the Rosh 700 years ago,” Rabbi Dayan replied. “The Rosh (Responsum 105:1), cited in the Tur and Shulchan Aruch (C.M. 185:1), ruled that if the seller stated a certain price and the agent sold the item for more, the additional money belongs to the seller. Thus, you should give the remaining $30 to Mendy.”

“But why?” asked Ezra. “How is this different from any other business, where the middleman buys and sells for a profit?”

“The reason is that you never bought the ticket,” explained Rabbi Dayan. “You were simply Mendy’s agent to sell it. Rabbi Kurz gave you the $180 for the ticket on behalf of Mendy.”

“And why not give the $30 back to Rabbi Kurz?” asked Ezra.

“There was no mistake on his part,” said Rabbi Dayan. “He was aware of the item he was buying and of the price he was paying. You were a diligent agent in getting the full price for the seller.”

“But why shouldn’t I be entitled to the $30 difference as a brokerage fee?” asked Ezra.

“A broker is entitled to a fee if he arranges it so ahead of time, or if that is the standard practice,” said Rabbi Dayan. “Similarly, had Mendy said, ‘Sell it for $150 and keep any extra,’ you would get the difference. Here, however, you simply sold the ticket to Rabbi Kurz on Mendy’s behalf, so the entire sum of $180 goes to him.”