We arrive at Mishnah 10 in the fifth chapter of tractate Bava Metzia. This Mishnah, the penultimate in the chapter, ties up a few loose ends that have not yet been discussed, and it contains three separate topics:
Exchanging labor for labor.
Early ribit and late ribit.
Verbal ribit.
Exchanging labor for labor:
The previous Mishnah dealt with "se'ah bese'ah", meaning exchanging goods for goods. The question that arises now is whether there is a concern for ribit when exchanging services for services. The answer is that there is indeed a problem here. If a person says to his friend: "Paint my house, which has four rooms, with me today, and tomorrow I will paint your house, which has five rooms, with you" - this is forbidden. This is a rabbinic prohibition, akin to fixed ribit, except that it is done with labor rather than money.
The reasoning behind this is that a worker's labor is measured by the workday and has monetary value, so the person gives value now and receives greater value later. This is not merely an exchange of favors, but a full-fledged monetary obligation: even if the house does not exist the next day to be painted, his friend is still obligated for the work done for him today. Since they are exchanging value for value here, this constitutes ribit.
Therefore, the Mishnah states what is permitted to do: "Omer adam lachavero: Nakesh imi va'anakesh imach, ador imi va'edor imach" - A person may say to his friend: Weed with me and I will weed with you, hoe with me and I will hoe with you. Today you will weed my field and tomorrow I will weed your field, today you will hoe with me and tomorrow I will hoe with you. This is exchanging the exact same thing, and is therefore permitted.
Even though with "se'ah bese'ah" there is a problem because the price of the goods might change, here the reasoning is that the value of labor is fixed. The Gemara defines a workday as lasting from sunrise to sunset, and workers take a fixed amount per day, and it makes no difference if one day is slightly longer or hotter than the other. People are not particular about these minor differences, just as we saw in the previous Mishnah regarding exchanging a loaf for a loaf.
In contrast, "Velo yomar lo: Nakesh imi va'edor imach, ador imi va'anakesh imach" - He may not say to him: Weed with me and I will hoe with you, hoe with me and I will weed with you. One may not exchange weeding for hoeing, because these are not tasks of the same type. Sometimes the value of weeding exceeds the value of hoeing, and sometimes the opposite is true, and since the values are not necessarily identical, such an exchange is forbidden.
"Kol yemei hagarid echad, kol yemei hareviah echad" - All the days of the dry season are one, all the days of the rainy season are one:
"Garid" means dry, and this refers to the summer season. All the days of this season are equal to one another: there is no difference in the difficulty of plowing on July 1 or July 2, and even if one day is slightly longer or hotter than another, people are not particular about it. Likewise, "all the days of the rainy season are one" - the same applies to the rainy season, where the wages for all its days are equal.
However, work in the rainy season is more demanding than work in the summer, since working in the mud is heavy and difficult, and therefore its wages are higher. For this reason, "Lo yomar lo: Charosh imi vagarid va'ani acharosh imach bareviah" - He may not say to him: Plow with me in the dry season and I will plow with you in the rainy season. Here the return is greater than the original service: the first work was done in the summer, which is easy and has lower wages, while the repayment is done in the winter, when the work is difficult and worth more. This addition is ribit.
From this, we learn that the opposite is permitted: it is permitted to say, "Plow with me in the rainy season and I will plow with you in the dry season", since the return is less than the original work.
A fundamental point: The entire prohibition applies specifically when exchanging services with a mutual commitment, and not when doing favors. If a neighbor helped you change a tire today, there is no prohibition to help him move a refrigerator tomorrow, since there is no defined expectation, neither explicit nor implied, to repay him measure for measure. In such a case, it is permitted.
Early interest and late interest:
From here, the Mishnah moves to a completely new topic: payments given to compensate the lender, except that they are given before the loan or after it. Since there is no existing loan at the time of the action, this is not a Torah prohibition but rather a rabbinic prohibition. What is given before the loan is called early interest, and what is given after it is called late interest, and the concept in both is the same.
"Keitzad? Nasan einav lilvos heimenu, vehayah meshale'ach lo ve'omer: bishvil shetalveini - zohi ribbis mukdemes" - How so? The borrower sets his sights on the lender, wishing to borrow money from him, and sends him a gift upon which he explicitly notes: this gift is being given so that you will lend me money later. This is interest in advance, and is rabbinically prohibited.
"Lavah heimenu vehechezir lo es hamaos, vehayah meshale'ach lo ve'omer: bishvil maosecha shehayu betelos etzli - zohi ribbis me'ucheres" - The borrower has already repaid his debt and there is no existing loan, and afterwards he sends a gift and notes that it is given in exchange for the lender's money that was lying idle and did not generate a profit. This too is rabbinically prohibited.
In both of these cases, the intentions were stated explicitly. However, the same law applies when the proximity in time between the gift and the loan is clear to all, or when the size of the gift is completely exaggerated relative to what is normal, as then it is obvious to everyone that it is being given in exchange for the loan, and the matter is prohibited.
Regarding the severity of the prohibition and the obligation to return the gift, we can distinguish three levels:
Fixed interest (Torah prohibition): The lender stipulates in advance, "I will lend you one hundred, provided that you send me a gift on my birthday." The rabbinical court compels the lender to return the gift.
Avak ribbis: Nothing was agreed upon in advance, but during the loan a gift is sent that is not customary between the parties, out of gratitude for the loan. The rabbinical court does not extract it from the lender, but to fulfill his duty to Heaven, it is fitting for him to return it.
Early and late interest: This is lighter even than avak ribbis, since at the time of the gift there is no existing loan at all. Therefore, the recipient is not obligated to return the gift even to fulfill his duty to Heaven: the giver indeed knows his own intention and performs an act that is rabbinically prohibited, but the recipient is removed from the matter and does not know what is going on.
Verbal interest:
The final section of the Mishnah deals with verbal interest: providing a benefit that is not monetary, is not economic, and is not tradable, but rather an emotional benefit that is provided through speech alone. Meaning, the lender gives one hundred dollars, and the borrower says something to him that gladdens his heart.
According to the version of the text that we have, this even refers to merely delivering good news: "Lo yomar lo: da ki ba ish peloni mimmakom peloni" - The borrower delivers good news to the lender that gladdens him, that a certain person has arrived in town. The very hearing of the news brings the lender joy, and if the borrower would not have bothered to deliver it to him had he not felt that he owed him a favor for the loan, the matter is prohibited, since he is bringing him pleasure and emotional benefit.
In the Jerusalem Talmud, a different version appears, which turns this into a different type of case: "He should not say to him: Find out if a certain person has arrived", and here it is the lender who is speaking to the borrower. He says to him: I will lend you the money without interest, but do me a favor and let me know if you hear anything about a certain person. It turns out that the borrower is providing him with a service, acting as a sort of private information service for him, and this is prohibited.
This line in the Mishnah is also the source for the well-known halachah that a borrower may not even say thank you to a lender for an interest-free loan, because the words of thanks give the lender satisfaction, which is an emotional benefit. This is brought as halachah in the Tur.
Contemporary poskim are much more lenient regarding this, including Rabbi Elyashiv and Rabbi Ovadia Yosef, for two reasons:
The expression of thanks is routine: It has no special significance, just as a person thanks someone who hands him something, even for an object he does not want. Receiving the check does not give the lender a tangible sense of satisfaction.
Thanking for time and effort: Beyond the actual interest-free loan, the lender invests time and effort sitting with the borrower, listening to him, drafting the document, and handling the collection of payments. It is appropriate to thank him for this, since no one is obligated to dedicate his time and effort to another person.
Therefore, one who wishes to satisfy all opinions should explicitly say: "Thank you for the time and effort you invested in organizing the gemach loan," since this expression of thanks is completely permitted.
What must never be done under any circumstances is to bless the lender, compliment him, or praise him. By doing so, the borrower does exactly what the Mishnah forbade: providing the lender with an emotional benefit in addition to the repayment of the principal. This is verbal ribis.
In summary: We learned three concepts in this Mishnah: Exchanging labor for labor is permitted when it involves the same work during the same season, but it is forbidden when the compensation exceeds the value of the original labor; early and late ribis are forbidden by the Rabbis even though no loan exists at the time, but there is no obligation to return them; and verbal ribis is forbidden even though it provides no monetary benefit, so one must not praise or flatter the lender, although it is permitted to thank him for his time and effort.