Ma'aser Sheni, Chapter 4, Mishnah 2. In the previous mishnah we learned that sometimes, when Ma'aser Sheni is moved from one place to another, its price changes. Our mishnah teaches that even in one and the same place the price may vary, depending on who is buying and who is selling.
"Podin ma'aser sheni k'sha'ar hazol" - Ma'aser Sheni is redeemed at the lower rate:
When there are two different prices in a single place by which the Ma'aser Sheni could be redeemed, the redemption is carried out according to the cheaper of the two, so that the Ma'aser Sheni does not gain so much. The mishnah brings two rules in this matter:
"K'mos shehachenvani lokeiach v'lo k'mos shehu mocher" - the calculation is made according to the quantity in which the shopkeeper, the retailer, buys from the wholesaler, where he receives a large amount of produce for less money; and not according to the quantity in which he sells, which is a small amount of produce for a lot of money, since in his selling he takes his profit. For example: if he buys at three dollars a pound and sells at four dollars a pound, the redemption is made at three dollars a pound, and the Ma'aser Sheni money set aside for each pound will be three dollars and not four.
"K'mos shehashulchani poret v'lo k'mos shehu metzaref" - when one comes to redeem perutos, the copper coins of Ma'aser Sheni, onto a silver coin, the calculation is made according to the rate of the shulchani, the money changer, when he receives the copper coins and gives a silver coin in exchange, for then he demands a large quantity of perutos; and not according to the way he himself gives out perutos in exchange for a silver coin, when he gives a smaller quantity. For example: if he demands one hundred perutos for every silver dollar, while when he is given a dollar he returns only eighty perutos, one must take one hundred perutos of Ma'aser Sheni in order to transfer them onto one silver dollar, which will now be the new Ma'aser Sheni money. That is, the calculation is based on one hundred perutos and not on eighty.
"Ein podin ma'aser sheni achsara" - Ma'aser Sheni is not redeemed by estimation:
"Achsara" means an estimate. Ma'aser Sheni is not redeemed on the basis of a mere assessment: one does not take a pile of grain, for example, without measuring it, without weighing it and without establishing its exact quantity.
Redemption by one and redemption by three:
Ma'aser Sheni produce whose value is known is redeemed on the word of a single witness. Some have the reading "al pi echad", without the word "eid", since this is not a matter of testimony but of expertise, and accordingly the meaning is redemption on the word of one expert.
But something whose value is not properly known must be redeemed on the word of three, who in effect constitute a court that establishes its value. These are the examples the mishnah lists:
Wine that has begun to spoil.
Produce that has begun to rot.
Coins that have begun to rust.
With these items it is difficult to determine the exact value, and therefore they require three to establish their worth.
In summary: in this mishnah we learned that the redemption of Ma'aser Sheni is made at the lower rate - at the rate at which the shopkeeper buys and not at the rate at which he sells, and at the rate at which the money changer receives perutos and not at the rate at which he gives them out; that one does not redeem by estimation but only by precise measurement; and that something whose value is known is redeemed on the word of one, while something whose value is not known - such as wine that has spoiled, produce that has rotted and coins that have rusted - requires an assessment by three.