Kilayim, Chapter Four, Mishnah One
Our mishnah and the next two mishnayot deal with empty patches within a vineyard and with the question of how large these empty patches must be before one can sow seed in them. There are two kinds of empty patches. The first is in the middle of the vineyard and it is called a karahat, or a bare patch.
The second is called a mehol and it is on the sides of the vineyard, adjacent to the fence. This patch need not be as large as the karahat in order for one to be allowed to plant there. According to Albeck, the word mehol is a reference to dances (meholot) that they would have there at the end of the harvesting season. Think of an ancient mishnaic square dance, with vineyards instead of haystacks!
1) A karahat [a bare patch] within a vineyard:
a) Bet Shammai says: [it must measure] twenty-four cubits [by twenty-four cubits].
b) But Bet Hillel says: sixteen cubits.
2) A mehol [an unsown belt of ground between a planted area and a fence] of a vineyard:
a) Bet Shammai says: [it must measure] sixteen cubits.
b) But Bet Hillel says: twelve cubits.
3) What is a karahat of a vineyard? A vineyard which has been cleared [of vines] in its middle.
4) If there are less than sixteen cubits, then one may not bring seed into it.
a) If it is sixteen cubits, they leave a space in which to work [the vineyard] and they may sow the rest.
Sections one and two: Before the mishnah discusses the law of a karahat or mehol, or even what these things are, it brings a debate between Bet Shammai and Bet Hillel concerning how large they must be in order to be considered a karahat or a mehol. As usual, Bet Shammai is the stricter opinion, with regard to both the karahat and the mehol.
Section three: As explained in the introduction, a karahat is a patch in the middle of a vineyard in which there is a clearing, meaning there are no vines.
Section four: If this patch is smaller than sixteen cubits (the opinion of Bet Hillel) then it is forbidden to sow seed there. However, if there are sixteen cubits by sixteen cubits, they can leave space in which to work the vines (four cubits on each side) and plant seeds in the middle. For instance, if the karahat is 16 by 16, he leaves four cubits on each side and he is left with an 8 x 8 patch 8 in which to plant seed.