Eduyos, chapter 1, mishnah 9. Before we turn to the mishnah itself, a preliminary remark is in order. This section of chapter 1 deals with mishnayos in which Shammai disagrees with Beis Shammai, and our mishnah is something of a puzzle - what is it doing here? For two reasons:
Shammai is not mentioned in it at all, so it does not contain the dispute that characterizes the rest of the mishnayos in this chapter.
The dispute in it is between Beis Shammai and Beis Hillel, with Beis Hillel taking the stringent position - and Eduyos devotes two entire chapters to mishnayos in which Beis Shammai are lenient and Beis Hillel are stringent, which is where this mishnah would properly belong, if anywhere.
Nevertheless, here it sits. There are indeed versions of the Mishnah that do not have this mishnah in this place, but in the text before us and in all the standard printed editions it appears here. It may be that it comes as a kind of introduction to the next mishnah, which also presents Shammai as against Beis Shammai.
Background: Maaser Sheni and redeeming it onto coins:
The subject of the mishnah is money that carries the sanctity of maaser sheni, the second tithe. Maaser sheni is the second tithe that the owner of the produce separates: after he has separated a portion of the crop for the kohen, called Terumah, and a portion for the Levi, called maaser rishon, he separates a further portion for himself - in the first, second, fourth and fifth years of the seven year shemittah cycle. In those four years he brings that tithe with him to Jerusalem in order to enjoy it there, presumably when he goes up for the festivals three times a year, at which point he brings his food along with him.
The Torah allows a person to redeem the sanctity of the maaser sheni food onto coins. A person says: I have no interest in hauling jugs of wine the whole way from my home, a two day journey from Jerusalem, so I would rather transfer the sanctity onto coins, and when I arrive in Jerusalem I will buy food with them. This is permitted, and it is the subject of our mishnah.
From small coins to a large coin:
But there is a question to clarify: what happens when a person gradually transfers sanctity from maaser sheni food onto small copper coins, and eventually finds himself holding a large sack of copper coins of considerable weight, and he wants to transfer all the sanctity of the copper coins onto a larger silver coin. Is this permitted? Halachically, the Rambam rules that one may not do so: once the sanctity is on coins, it must remain on coins. There is a qualification, a kind of limiting condition that we will see later on, under which one may in fact do so. In any case, our mishnah deals with converting copper coins into silver coins, which does indeed work when it is done in this way.
The concern: a shortage of copper coins in Jerusalem:
The concern is that if people do not bring small copper coins to Jerusalem but only one large silver coin - like someone who shows up with a hundred dollar bill - it is certainly efficient, but if everyone does this there will be a shortage of copper coins in Jerusalem. Everyone will be holding coins of enormous value, everyone will want to break them into change and will not be able to, and the exchange rate between the large silver coins and the small copper coins will be thrown out of balance. People will not be able to buy enough copper coins with their money, and the end result will be that they have less money available for purchasing maaser sheni food, and consequently less maaser sheni food will be available to the festival pilgrims.
And that is a bad outcome, because the Torah wants a person to have a sense of abundance and wealth when he comes to Jerusalem. He goes up to Jerusalem, he is inspired, he visits the Beis HaMikdash, he connects to Hashem, he brings his offerings, he sees the daily tamid and all the great things happening there - but part of the picture the Torah intended is that he should have enough food for the seven days. It is like a great celebration, in which the spiritual elevation and the physical celebration go hand in hand. If there are not enough small coins in circulation, prices will rise or the value of the money in his hand will drop - a kind of inflation - and the end result will be that he has less food, and that reduction in maaser sheni is not what the Torah wants and not what the Sages want.
So the question is: may a person convert all the copper coins in his possession into silver coins, and thereby possibly cause this problem, that he will not be able to obtain enough copper coins when he comes to make the conversion back in Jerusalem?
The dispute between Beis Shammai and Beis Hillel:
The wording of the Mishnah: "HaPoret sela mi'ma'os ma'aser sheni" - a person who wishes to gather his small ma'aser sheni coins into a sela, the largest of the silver coins. One sela contains seven hundred and sixty-eight small copper perutos, which is obviously a very large quantity. Concerning this, "Beis Shammai omrim b'chol ha'sela ma'os" - there is no problem with it at all, and one may convert all seven hundred and sixty-eight small copper coins into a single large sela. Beis Shammai are not concerned about the difficulty of converting the money back when he arrives in Jerusalem.
It is worth noting that the word "poret" is used in our Mishnah in an unusual sense. Normally "poret" means breaking something down into its parts - like the word 'prit' (item) in modern Hebrew - that is, taking a large coin and breaking it into small coins. In this Mishnah, however, "poret" means the opposite: combining many small coins into one large coin.
In contrast, "u'Veis Hillel omrim b'shekel kesef u'v'shekel ma'os" - he should do it half and half, so that copper coins remain in his possession. This is a kind of compromise: the weight he has to carry is reduced, since part of the copper has been converted into silver, which is denser in value, and at the same time he will still have copper coins when he arrives in Jerusalem, so no problem of shortage will arise.
And to explain the wording: "b'shekel kesef" - the value of a shekel out of the sela, for there are two shekels in one sela, so that a single shekel is a medium-sized silver coin. "u'v'shekel ma'os" - the second half, which could also have been converted into silver coins, he must leave as ma'os, as copper coins. And the halachah follows Beis Hillel, that one should do it half and half.
The second part of the Mishnah: combining money and produce:
The second part of the Mishnah presents a new point, regarding combining coins one upon another. The rule is that a person may not take two silver shekels of ma'aser sheni money and convert them into one large sela, since that is not the purpose of redemption. This is not a game of transferring sanctity from place to place: the permission is to move from foods to coins, but the Sages did not want coins transferred to other coins. Moreover, in every conversion he is liable to lose some of the value and to pay a kind of exchange fee and commission to the money changer, and we do not want that to happen unnecessarily. The question, then, is whether one may move from small silver coins to medium-sized silver coins.
Rabbi Meir says: "Ein mechallelin kesef u'feiros al hakesef" - one may not do so, even in the following case: he has an ordinary sela coin that is not consecrated; he has one shekel, half a sela, upon which the sanctity of ma'aser sheni rests; and he also has foods - let us say bottles of ma'aser sheni wine - worth a silver shekel. He might say: I have one large coin, and I will transfer onto my sela both the shekel coin and the shekel's worth of wine together. Seemingly this is not a game of moving from two coins onto a large coin, since essentially he is transferring food onto a coin, and it is only because the value of the food does not amount to the full value of the large coin that he makes up the shortfall by adding another ma'aser sheni coin. To this Rabbi Meir says: this too may not be done. One does not redeem a silver coin that carries the sanctity of ma'aser sheni, such as a half-sela silver coin, together with ma'aser sheni produce and foods, onto one large silver coin.
And the Sages say that it is permitted. That is, we do not like taking two silver coins and transferring them onto one large silver coin, but if he has one silver coin plus the value of one silver coin of ma'aser sheni, and these combine together, he may transfer them onto a larger silver coin. Such is the opinion of the Sages, except that this is limited up to the value of a dinar. The dinar is a quarter of a sela, that is, half a shekel, and it was the standard silver coin in use. The idea is that if a supplement is needed - coins plus produce in order to reach a dinar - that is permitted. But one who has a full dinar does not need to take a full dinar plus food in order to reach a shekel, or a full shekel plus food in order to reach a sela. Up to amounts of one dinar, he may combine smaller silver or copper coins together with foods.