Arachin, Chapter 3, Mishnah 2. The chapter opened by listing the cases in which a single law can turn out either lenient or stringent depending on the circumstances. Now the mishnah takes those cases one at a time and shows us how. The first of them is the redemption of a sdeh achuzah, an ancestral field that had been consecrated to the Beit Hamikdash.
What exactly is a sdeh achuzah? It is land that came to a man by inheritance. When Bnei Yisrael entered Eretz Yisrael under Yehoshua bin Nun, the country was divided among the tribes and families; his family received its portion then, and that portion passed from father to son until it reached him. Should he dedicate such a field to hekdesh, so that it becomes property of the Beit Hamikdash, and later decide that he wants it back in his hands, the amount he pays has nothing to do with what the field is worth. The Torah names a price, and that is the price he pays, whether the plot is valuable or nearly worthless.
Leniency and stringency in one law
The mishnah states: "Bisdeh achuzah lehakel ulehachmir." When a consecrated ancestral field is redeemed, one and the same rule can work out in the owner's favor or against him. "Keitzad?" In what way? Picture two men who consecrate fields. Of the first the mishnah says "echad hamakdish becholat hamachoz": he dedicated sandy soil on the outskirts of the town, ground that passersby tread across as they come and go, land that fetches almost nothing. Of the second it says "ve'echad hamakdish bepardessot Sevasti": he dedicated a plot among the orchards of Sevasti, the city Herod built in the Shomron with its magnificent gardens, soil of the finest quality and the highest price. For both of them the Torah rules the same way: "noten bezera chomer se'orim chamishim shekel kessef." Any stretch of ground large enough to be sown with a chomer of barley, and a chomer equals thirty se'ah, is redeemed for fifty silver shekel. Fifty, for each such measure of land. On top of that the owner adds a fifth when he redeems. But the basic figure never budges, not for the cheap ground and not for the costly ground.
This flat rate holds where the consecration and the redemption both fall at the opening of a fifty year Yovel cycle, in its first year. The masechet takes up this qualification later on and works it through in detail.
The purchased field
"Uvisdeh miknah noten et shovyo." Suppose, though, that the field never came down to him through his family at all; he acquired it by purchase, and then consecrated it. To bring that field back into his own possession for his own use, he must pay whatever it is worth on the market.
Set the two side by side and you see where the leniency and the stringency lie. The purchased field is always redeemed for what it is worth. The ancestral field is redeemed for the set fifty shekel. So if the ancestral field he is buying back from the Beit Hamikdash is inferior ground, and he must nevertheless hand over fifty shekel, he is paying more than the field is worth, and the fixed rate has come out stringent. And if the ancestral field is choice, expensive land, and he pays only that same fifty shekel, the fixed rate has come out lenient.
Two points to keep in mind
First, an ancestral field returns of itself to the family that inherited it, even though the owner had consecrated it to the Beit Hamikdash. When Yovel arrives, ownership reverts automatically to the original family. Our whole discussion, then, concerns the years leading up to Yovel.
Second, when we speak of the market value at which a purchased field is redeemed, that valuation rests on several variables: the size of the field, the quality of its soil, and how many years remain until Yovel. For at Yovel this field too must be returned to the family that received it in the days of Yehoshua bin Nun. Land always finds its way back to its original owners at Yovel, and the price of redemption must reflect that.
The view of Rabbi Eliezer
"Ribbi Eliezer omer: echad sdeh achuzah ve'echad sdeh miknah." In Rabbi Eliezer's opinion, both kinds of field, the inherited one and the bought one, leave hekdesh for the Torah's set price of fifty silver shekel per area sown with a chomer of barley. But if the payment is identical in both cases, "mah bein sdeh achuzah lisdeh miknah?" what is left to separate them? The Torah presents them as two distinct laws, so something must set them apart. Rabbi Eliezer's answer: "Ella shebisdeh achuzah noten chomesh, uvisdeh miknah eino noten chomesh." The one and only distinction lies in the fifth. Redeem your inherited field and you add a fifth to the sum; redeem a field you once bought and no fifth is due. According to him nothing else divides the two: the same fifty shekel goes to the Beit Hamikdash in either case, and the chomesh attaches to the ancestral field alone.
The Tanna Kamma, the first opinion voiced in the mishnah, sees it differently. Granted, the fifth belongs to the ancestral field and is never charged on a purchased one, but the differences do not end there. The way the payment itself is figured is also not the same: the inherited field goes out for the Torah's flat sum of fifty silver shekel, while the purchased field goes out for whatever the land is worth on the market.