“We are pleased to announce that we have been donated a car for communal use,” read the sign in Kollel Mishpat. “The car gemach (loan service) will be run by Dani.”

“I have an appointment next Tuesday,” Yossi said to Dani. “Is the car available then?”

“Yes,” said Dani. “The charge is fifty cents per mile to cover gasoline and wear and tear, due immediately upon returning the car. If you fill up with gas, the gemach refunds that amount.”

Yossi picked up the keys on Tuesday afternoon. “I should be back in about five hours,” he said.

“There’s not much gas in the car,” said Dani. “You’ll probably have to add gas on the way home.”

Yossi drove to his appointment 30 miles away. On the way home, he pulled into the gas station.

“How much gas should I put in?” Yossi thought to himself. He checked his wallet. “I’ve only got $40 cash. Should I put in $10, $20, or $30?” After some deliberation, he paid the attendant and proceeded to the pump.

Yossi returned just before Mincha. He gave the keys to Dani, and said, “I’ve got to run to mincha now! We’ll settle later.”

A month later, Dani called Yossi. “I was reviewing the car log,” he said. “You drove 60 miles, which is $30, but no payment is listed.”

“You’re right,” Yossi apologized, “I forgot to take care of it, but I purchased gas.”

“That’s fine,” said Dani. “How much did you put in?”

“It’s funny, but I don’t remember anymore,” said Yossi. “I remember debating, though, whether to put in 10, 20, or 30 dollars.” He tried unsuccessfully to jar his memory.

“It’s a pity you didn’t pay on time, like you were supposed to,” said Dani. “Then we wouldn’t have had this problem. Ask Rabbi Dayan how to deal with this!”

Yossi called Rabbi Dayan. “I owe the car gemach $30, but purchased gas on the way home,” he said. “I don’t remember, though whether I added $10, $20 or $30. Should I assume the least, most, or middle amount?”

“This issue seems to be an intricate dispute between the Ketzos Hachoshen and the Nesivos Hamishpat,” said Rabbi Dayan, “although there is an additional factor here.”

“Oh?” said Yossi. “I didn’t think it would be so complicated.”

“In general, when neither the lender nor the borrower remembers whether the loan was repaid,” explained Rabbi Dayan, “the person cannot be made to pay in beis din, and there is even a dispute whether he has a moral obligation to pay, latzeis yedei shamayim (see Taz 75:10; Shach 75:65-67; Pischei Teshuva 75:21).”

“This seems to be our case,” said Yossi. “Neither of us knows whether I repaid the loan by purchasing the gasoline.”

“It seems so at first,” said Rabbi Dayan, “but our case is somewhat different. You have a definite obligation of $30 for using the car, which you did not repay, and there is a possible counter obligation of $10-30 for the gas you bought,” said Rabbi Dayan. “The Ketzos Hachoshen (75:5) differentiates between a possible repayment and a counter obligation. When there are two counterclaims, the Ketzos reasons that we treat each obligation independently. The obligation of $30 is clear, whereas the counter obligation for the gasoline is questionable, so that we have to assume the minimal amount of $10. As such, you remain obligated to pay $20.”

“You mentioned that the Nesivos argues?” said Yossi.

“Yes. The Nesivos Hamishpat (75:5) reasons that the counter obligation is considered a form of repayment,” said Rabbi Dayan. “As such, this case is also considered one of possible repayment where neither party knows, so that there remains, at most, a moral obligation.

“Nonetheless, in this particular case, there is an additional reason to obligate you,” concluded Rabbi Dayan. “This is because the uncertainty arose because of your negligence. In a normal situation where neither the borrower nor the lender remembers whether the loan was repaid, both parties are equally at fault. It is understandable that people sometimes forget. Here, however, had you paid in a timely manner according to the rules, you would have known how much you spent on gas. Only because you delayed so much did the doubt arise, so you cannot hide behind the veil of forgetfulness. Therefore, you can assume only the lower amount of $10, and must repay the remaining $20 (see Pischei Choshen, Halva’ah, ch. 2, note 78; Nesivos 75:5).”