Currency fluctuations can wreak havoc on people’s finances. Many investors and lenders sustained large losses with the recent plunge of the Russian ruble. When lenders granted ruble-denominated loans, even if they are repaid the entire face amount of their loans, the value and purchasing power of such repayment is substantially lower than the value at which the loan was originated. An American investor who purchased Russian bonds just two months ago lost around 20% of his investment simply because of the exchange rate fluctuations. Similarly, Russian homeowners who had outstanding foreign currency mortgages now pay substantially more rubles to service their loan.
Of even greater concern to the Torah Jew are the potential ribbis violations present in foreign currency transactions. These challenges apply to all of us, not just to the international businessman. People often borrow shekels from a friend or neighbor in the US for use when they arrive in Eretz Yisroel. There is no interest on the loan; they intend to simply repay with the same amount of shekels upon their return. This seemingly innocent transaction likely violates hilchos ribbis, as we will explain. Another seemingly innocuous case would be a dollar-based, non-interest-bearing loan between two individuals in Eretz Yisroel. This too can pose serious ribbis concerns.
In order to understand the issues at hand, we must first introduce certain basic tenets of hilchos ribbis.
Ribbis that is prohibited min haTorah (biblically prohibited) is generally referred to as “ribbis ketzutzah,” meaning that the interest was set at the time the loan was initiated. However, in order to safeguard against violating ribbis min haTorah, Chazal extended these prohibitions to certain other transactions and loans. There are many forms that are included in this category, but one in particular is pertinent to the issue at hand:
Seah B’seah (Measure for a Measure)— Although lending out goods for repayment in kind is perfectly permissible according to Torah law (since the lender is receiving the same quantity of goods that he lent out), Chazal forbade such transactions. The reason for this prohibition is that if the price of the goods appreciates at the time of repayment, the lender will profit from the transaction. For example, if someone lent 100 ounces of silver when it was trading at 10 dollars an ounce, and was repaid in kind when it was valued at 12 dollars an ounce, the lender will have earned two hundred dollars from the transaction, despite the fact that he received the same weight of silver he initially lent. Although the profit was a result of a price fluctuation, and the price was just as likely to decrease, nevertheless Chazal prohibited such transactions.
Currency or Commodity
The prohibition of seah b’seah does not apply to local currency: If a person in the United States borrows one hundred US dollars, he may repay the same hundred dollars even if there was deflation and the purchasing power of the money increased at the time of repayment. The prohibition does not apply to currency, and is only applicable to items defined as “peiros” (literally, fruits), i.e., goods. The reason for this is that currency is treated in halacha as having a fixed value. Therefore, when prices increase, we view the increase as a change in the value of the peiros/goods, and not as a decrease in the value of the currency. By this definition, a lender who receives the same amount of currency he lent out is not considered to have made any profit off the transaction, regardless in the change in price levels. Rather, it is only when lending and receiving goods whose value appreciated during the course of the loan that a lender can be halachically deemed to have received more value than he lent out.
This distinction between currency and goods leads to some fascinating questions. In the US, it is easy to define currency — the US dollar. However, in the times of the Gemara, currency in most countries consisted of gold, silver, and copper coins. These coins, even if minted in the same country, constantly fluctuated in their relative values. For example, the exchange rate of copper coins to silver coins would vary on a regular basis (unlike today, when a quarter is always twenty-five cents and a nickel is always five cents). The question that arose was which coins were considered currency — the gold coins, the silver coins, or the copper coins? The Gemara tells us that only silver coins were considered currency, while gcy rates only on a daily basis, this is sufficiently stable to qualify for yatza hasha’ar. Others argue that even daily fluctuations are not considered as stable.
However, there is another important issue: In the times of the Gemara, price instability was indicative of a lack of supply. Without regular availability, the borrower could not be considered in theory as having the product in hand (yesh lo); therefore, the problem of seah b’seah would apply. Today, however, regular fluctuations in terminally-traded markets (such as currencies) are generally not due to a lack of availability. On the contrary, the fluctuations occur because of minute shifts to the supply and demand equilibrium. At the market price, freely traded currencies are virtually always available in significant quantities. Since the supply of currency is readily available, despite the fluctuating price, the problem of seah b’seah should not apply. This, however, holds true only if stable pricing was required only because it was indicative of ready supply. If however, the leniency of stable prices is not because of availability, but rather because stable prices allow the borrower to replace the material before the price appreciates, currencies, whose price fluctuates extremely rapidly, would not qualify for the leniency. This question seems to be a matter of dispute among both the Rishonim and Achronim.
This discussion illustrates some of the challenges in applying halacha to modern-day scenarios. As commerce evolves, it is important to be sensitive how these shifts impact halacha. It also illustrates how seemingly insignificant factors can materially affect the halachic status.
As such, the purpose of this article is to create awareness of the halachic issues, and to stimulate discussion. It is not intended to be used for a psak halacha, and one should consult a competent halachic authority before engaging in such transactions.
 Some are of the opinion that in certain instances, even ribbis that was arranged subsequent to the loan can be a violation of Torah law (Rashi, Bava Metzia 68a, s.v. “velav milsa”; Shulchan Aruch 164:1; Shach 164:2).
 Bava Metzia 45a. The rationale for this will be explained later.
 See however, Minchas Shlomo Vol. 1, 27:4 (also quoted by, Nesivos Shalom p. 250) who suggests that nowadays, seah b’seah would not apply to currencies since all forms of legal tender are valued solely based on their worth as a currency (representative value) and not based on their material (intrinsic) value. As such, they are never classified as a commodity.
 Teshuvos HaRashba 4:287; Chazon Ish, Yoreh De’ah 72:9. However, the Ritva (Bava Metzia 44a, s.v. “vechol hametaltelin” disagrees.
 Section 2:54
 HaRav Mendel Shafran, shlit”a, in Hayashar Vehatov Vol. 18, pp. 21–23. See Nesivos Shalom p. 250, who quotes HaRav Elyashiv zt”l
 Shulchan Aruch, Yoreh Deah 162:2
 Ibid., se’if 3
 Shevet HaLevi Vol. 3:109
 Mishnas Ribbis 6n12, quoting HaRav Elyashiv zt”l
 Bais Yosef (Tur, Yoreh Deah 162), citing Teshuvos Rashba Chadashos 76; Ba’al HaMaor, Bava Metzia 45a (dapei haRif); Sha’ar Deah 162:3