Bava Basra, Chapter 1, Mishnah 6. In this Mishnah we discuss properties held in partnership, and how and when the partners may force the division of the property upon one another.
Dividing the Courtyard:
The Mishnah begins: "Ein cholkin es hachatzer ad sheyehei arba amos lazeh ve'arba amos lazeh" - one partner cannot force his friend to divide the courtyard and erect a wall in the middle, unless four amos remain for each of them.
In the first Mishnah of the chapter we learned that if the partners agree to divide, they are permitted to divide even a small courtyard. Here, on the other hand, we are speaking of a forced division, and it requires that a usable area remains for each of the parties. The Mishnah establishes this measure at four amos, and this is its meaning:
Four by four amos in front of the entrance - an area a person needs in front of the entrance to his house, for unloading a donkey and the like. This is like a private square at the entrance, and it is not included in the calculation of the courtyard.
Four by four amos of the courtyard - the shared area required for a person for cooking, preparing things, and cleaning them.
It emerges that the total area of the courtyard must be four times an area of four by four amos: four by four amos is sixteen square amos, and altogether sixty-four square amos. This is because each of the partners receives two areas of four amos - eight by four amos - the four by four in front of his entrance and another four by four of the courtyard. If the courtyard does not contain sixty-four square amos, including the entrances, a person cannot force his neighbor to divide the place in two, since the parts will not be usable.
Dividing the Field:
"Velo es hasadeh ad sheyehei tishah kavin lazeh vetishah kavin lazeh" - the same applies to partners who hold a field together and wish to separate: if the field is too small to serve as two half-fields, one cannot force his friend to divide it. And how large must the field be so that it remains usable even at half its size? The Mishnah says: nine kavin.
This measure requires explanation. The kav is a measure of volume - about two liters - and expresses capacity, a three-dimensional space; whereas here we are speaking of a two-dimensional area. The meaning is therefore the area of a field required to sow a quantity of nine kavin of seeds, such as wheat kernels.
The standard measure for area is called a 'beis se'ah'. The se'ah is also a measure of volume - six kavin. A beis se'ah is an area of fifty by fifty amos, and it holds six kavin. Nine kavin, as in our Mishnah, are therefore a beis se'ah and a half - about thirty-seven square amos, which is approximately one thousand square meters: one dunam in the Land of Israel, or about ten thousand square feet. For illustration: this is the size of an Olympic swimming pool, or about three tennis courts, or exactly four doubles tennis courts inside the lines. With less than this, there is no economic sense in growing grain.
"Rabbi Yehudah omer, ad sheyehei bah tishas chatzi kavin lazeh vetishas chatzi kavin lazeh" - according to Rabbi Yehudah, half the measure is sufficient, four and a half kavin for each of the parties. The reason for this: in Rabbi Yehudah's location the land was particularly fertile, and therefore even a relatively small area was worthwhile. There is no fundamental dispute here, as the rule is agreed upon: the division must be economically viable.
The Gemara adds that in Babylonia, where the land was even less fertile, a plot large enough to require a full day of work for plowing the field and the like is needed. Hiring workers is done for a full day, and if the plot does not contain a day's work - the field owner ends up paying a full day's wage and does not receive a full day's work in return, and this is not worthwhile. Therefore, this measure is required at the very least.
Dividing a garden:
"Velo es haginah ad sheyehei bah chatzi kav lazah vachatzi kav lazah" - When dividing a jointly owned vegetable garden, a much smaller area is sufficient: a little over two hundred square amos, which is roughly six hundred square feet or sixty square meters - about the size of a small apartment. The reason for this is that vegetable gardens are much more profitable, since large produce can be grown in small areas.
"Rabbi Akiva omer, beis rova" - A quarter of a kav, which is one twenty-fourth of a beis seah. More precisely, one hundred and six square amos, which is about thirty square meters - a small area, about the size of a large room.
Other properties:
The Mishnah continues by listing other properties whose division cannot be coerced:
"Velo es hatraklin, velo es hamoran" - Joint ownership of a large hall, such as an assembly hall or banquet hall.
"Velo es hashovach" - A dovecote for raising and breeding doves and pigeons.
"Velo es hatalis" - A garment or cloak.
"Velo es hamerchatz" - A bathhouse.
"Velo es beis habad" - An olive press.
In all of these cases, a person cannot force his partner to divide the property, "ad sheyehei bahen kedei lazah uchdei lazah" - unless they are large enough that even after being divided in two, each partner will be left with a proper, usable portion.
"Zeh haklal":
What is the defining parameter for this? "Zeh haklal: kol sheyechalek ushmo alav - cholkin, ve'im lav - ein cholkin" - Anything that will still be called by the exact same name even after it is divided in two, its division can be coerced; but if not, they do not divide. To illustrate:
A bathhouse: If it has two mikvahs inside, each partner can take half and be left with a mikvah, so the name "bathhouse" still applies to it. But if it contains only one mikvah, and they divide it - two halves of a mikvah amount to nothing.
A talis: If it has the required size of a talis, but once it is cut in half it will merely become a scarf - it is too small to still be called a talis.
Gud o agud:
The conclusion that emerges from these matters: If a property is large enough to be divided in two, one may turn to a beis din and coerce its division. But for a property that is too small for division and will not be usable as a half, such as a small field, a bathhouse, or the like, the rule learned here applies. This is known as "gud o agud" - either you take it all, or I take it all.
This is done by setting a price. One of the partners says to the other: "This tallis is worth one hundred - either you give me fifty and take the whole thing, or I will give you fifty and take the whole thing," since it is impossible to continue functioning in a partnership. He has the power to force this, and the choice is given to the second partner: to take the whole thing, or to pay for half according to the set price.