The Goldin family sat down for their Shavuos milchig meal and eagerly awaited the rare opportunity to eat challah with butter at a Yom Tov meal.
“Where’s the butter?” Mrs. Goldin muttered to herself as she searched the fridge.
“It seems that we forgot to buy butter,” Mrs. Goldin finally said to her family.
“Maybe we can get from the neighbors,” suggested Mr. Goldin.
“I’ll try the Millers across the hall,” replied Mrs. Goldin.
Mrs. Goldin knocked on the Millers’ door. “Gut Yom Tov,” she said. “Do you have any butter?”
“We bought extra; we can certainly give you some,” replied Mrs. Miller. “We’re having milchig tomorrow and I forgot to buy cream cheese. We even have lox, but no cream cheese!
“We have a container of cream cheese, but we’d rather have butter,” said Mrs. Miller. “They’re worth about the same. If you give me butter, I’ll give you cream cheese.”
“That’s fine with me,” said Mrs. Miller. “Take the butter now, and we’ll get the cream cheese from you tomorrow.”
Mrs. Goldin returned to her apartment. “I got butter,” she announced, “and agreed to give them our cream cheese in exchange.”
“But I wanted cream cheese,” complained Simcha. “I’m sure other people have extra. I’ll find them a cream cheese for tomorrow.”
“I don’t know that you can use the cream cheese anymore,” said Mr. Goldin. “Once Mommy traded the butter for the cream cheese, maybe it’s already theirs.”
“How could it be theirs?” asked Simcha. “It’s still sitting in our fridge! What’s the big deal? I’ll use the cream cheese now and get another one for them tomorrow.”
“I can’t allow you to use it,” insisted Mr. Goldin. “Tonight, we can ask Rabbi Dayan at the learning program.”
During a break between shiurim, Mr. Goldin and Simcha approached Rabbi Dayan and posed their question. “Could we have used the cream cheese?” Mr. Goldin asked.
“What a relevant question for Shavuos!” exclaimed Rabbi Dayan. “This halacha is rooted in Megillas Rus, which teaches us the halacha of kinyan chalipin, exchange.”
“I thought chalipin was a symbolic exchange,” said Simcha. “Like with a handkerchief or pen.”
“Chalipin is a symbolic act indicating sincere intent to validate a transaction,” explained Rabbi Dayan. “It requires something similar to a shoe, e.g., an article of clothing or a functional utensil. Food cannot be used to facilitate chalipin.” [Choshen Mishpat 203:1]
“Nonetheless, the Mishnah [Bava Metzia 100a, 46b] discusses chalipin of two animals,” continued Rabbi Dayan. “Some explain that an animal is similar to a utensil since it can be used for work. However, Rabbeinu Tam maintains that there is a second form of chalipin: barter of equivalent items. This chalipin can be done with food too so that if one food item is given as barter for another, the other item is immediately acquired by the second party.”
“What is the halacha?” asked Simcha.
“The Rema cites two opinions whether barter with a food item immediately transfers ownership of the other item,” answered Rabbi Dayan. “The Gra sides with the opinion that it does; the Mechaber seemingly indicates so, as well.” [Choshen Mishpat and R’ Akiva Eiger 203:3; Gra 203:11]
“Some suggest that even according to the opinion that the other item is not acquired immediately,” added Rabbi Dayan, “the first party still has a binding obligation to give it.” [Machaneh Ephraim, Hil. Davar Shelo Ba La’olam #3; Pischei Choshen, Kinyanim 7:16-17]
“Do the items have to be of equivalent value?” asked Mr. Goldin.
“Some indicate that the items must be valuated,” replied Rabbi Dayan. “However, it seems that as long as the parties agreed to barter the items, either because of similar value or respective need, it is considered barter of equivalent items.”
“Thus, when Mrs. Goldin took the butter,” concluded Rabbi Dayan, “according to most authorities the Millers immediately acquired the cream cheese. You at least have a binding obligation to give it to them. You may not use it.”