Nachum was doing a research project on the Rambam for one of his shiurim. He borrowed a number of sefarim from his yeshiva’s library for a month. When he completed the assignment, he gathered the sefarim to return them, but noticed that one sefer was missing.

“Where could it be?” Nachum asked himself. He asked his family whether they had seen the sefer anywhere, but no one had seen it.

“I’m returning the sefarim I borrowed a month ago,” Nachum said to the librarian. “I seem to have lost one sefer, though.”

“You’ll have to pay for it,” said the librarian. “Which one was lost?”

“It was a new, precise edition of the Yad Hachazakah,” replied Nachum. “How much does it cost?”

“That sefer runs about $50,” said the librarian. “It was a bit expensive.”

Nachum thought for a moment. “I can get an almost brand-new copy,” he said. “I have a relative who mentioned that he has a spare copy and once offered it to me.”

“Actually, we have three other copies of that sefer,” said the librarian. “We don’t really need a fourth copy of that particular edition and would like the cash.”

“But why should I do that?” replied Nachum. “I can get the book for free from my relative!”

“When you lost the book, you became obligated to pay for it,” the librarian stated. “You owe us money and can’t give a book instead of payment.”

“Why do I owe you money?” argued Nachum. “I borrowed a sefer. Had I not lost it, I would have simply returned it. What’s the difference whether I return that, or a comparable copy?”

“If you were returning the original, fine!” insisted the librarian. “However, now that you lost it, you need to pay, and we’ll do with the money as we see fit!”

“That doesn’t seem logical,” responded Nachum. “I’d like to discuss the case with Rabbi Dayan.”

“Fine with me,” said the librarian. “Let’s go!”

The two went to Rabbi Dayan.

“l borrowed a special edition of Yad Hachazakah from the library and lost it,” explained Nachum. “The library wants me to pay cash for it, but I can get a free copy from my relative. Can’t I just give back that copy and not pay cash as the librarian demands?”

“You can return another copy of the book,” ruled Rabbi Dayan, “provided that it is in comparable condition to the one you borrowed.”

“Why is that?” asked the librarian.

“There is a significant discussion in a case of damage whether the primary responsibility is to repair the damage or to pay compensation for the monetary loss,” explained Rabbi Dayan. “We’ll leave that particular discussion for another occasion, but it seems clear that a borrower’s primary liability is to return the borrowed item or its replacement.

“Furthermore, the Shulchan Aruch and most authorities rule that even a thief or one who damages can pay with movable items (metaltelin) in lieu of cash,” added Rabbi Dayan. “The logic is that such items can easily be sold and converted to cash. We evaluate the item according to how much it can be sold for at that time and place (B.K. 7b; C.M. 419:1, 101:9).

“Nonetheless,” concluded Rabbi Dayan, “if a library has clear terms that lost books must be paid for by cash value, those terms would be binding, as any other monetary agreement.”

“I’m wondering about another point,” Nachum said. “What if the borrowed item changed price between the time it was borrowed and when it was lost? Which price would you pay?”

“On this point, there is a difference between a thief and a borrower,” answered Rabbi Dayan. “A thief pays the item’s value at the time of the theft, unless he returns it intact. A borrower, however, pays the item’s value at the time that it was lost. This is because the item remained the owner’s until then and also because the borrower committed to pay the item’s value at the time he becomes liable (C.M. 362:1; Ketzos and Nesivos 291:1).”

Our store had a sale where everything was 10% off. However, due to a clerical error, one item scanned at the regular price without the deduction.

None of our customers realized that 10% was not deducted from that item and they paid the regular price.

Q: Are we obligated to refund that 10% to those customers since we charged them our standard price, or may we keep it?

A: It seems from your question that you are looking at the issue from the perspective of onaah — the prohibition against exploiting someone in the context of a sale. Accordingly, you are suggesting that since the customers paid the regular price, they were not exploited.

However, the issue is not onaah; the issue is that there was an agreement to charge a certain amount for that item and the customers were charged more than that. Charging a customer more than the agreed amount is a form of theft. The customers must be contacted so that they can retrieve their money.

Therefore, if you have a record of all the customers who bought that product and did not receive the 10% discount, you must contact them in order to refund the money. Although the theft was inadvertent, it must nevertheless be refunded. However, it is sufficient to contact them and inform them that they may come and pick up their refund; you are not obligated to go out of your way to deliver or even send a check to each of these customers (C.M. 367:2).

If some of the customers have an account in your store and you want to just credit their account, you may do so without informing them of the error. Customers that may not come to the store again must be contacted and informed that they are owed money (C.M. 355:1).

In the event that you do not have a record of who purchased this item and even after posting notices that customers who purchased this item should come in for a refund, you still have money that was not refunded, that extra money should be used for tzorchei tzibbur — community needs (C.M. 366:2).

For example, the money could be donated to Hatzolah or the local mikveh; simply giving it to a local tzedakah organization is not sufficient (Igros Moshe, C.M. 1:88).

Using the money for community needs effects partial atonement for the transgression, since it is possible that the victims of the theft will benefit from that money (Sema 366:5).

By using the money for the benefit of the community, it is hoped that Hashem will arrange circumstances so that the victims or the victims’ heirs will benefit an amount equal to what the victim was owed, and we know that one who strives to purify himself will receive Divine assistance in that pursuit (Aruch Hashulchan 366:3).

Q: If I find a credit card or ring of keys, what should I do with them?

A: If you do not recognize the name on the card, you should publicize that you found a credit card, and require that the claimant identify himself by name. Alternatively, you can mail the card to the company’s address listed on the card.

If time passed since the card was lost, so that the owner certainly canceled the card, you can destroy it and dispose of it (see Shulchan Aruch Harav, Metzia #30; C.M. 262:1; Sema 261:2).

If you find a ring of keys, you should publicize it, and the number of keys or an identifiable key ring serves as a siman.

If the key is a loose one, if the person can show an identical key, that serves as a siman. It is also possible to give him the key to check if it fits his door; if not, he should return it to you.

If a long time passes and no one comes to claim the key, so that the owner likely changed the lock, some authorities allow you to dispose of the key (C.M. 262:3, 16; Hashavas Aveidah K’halachah 12:14-15).