Here we’ll talk about a situation where the seller is selling only part of his field, but doesn’t specify which part he is selling and which part he is keeping for himself. The Mishnah says: Someone tells his friend, “I’m selling you half of my land,” but doesn’t tell him which part of the field he is selling. We divide the quality between them. We divide the land into two parts of equal value, and the seller can basically choose whichever part he wants. He has told the buyer that he is selling him half the land. That really means half the value, but he hasn’t told him which parcel of land he is giving over to him. Therefore, from the seller’s perspective, he can always say, “This is the land I was selling you. This is the land I was keeping for myself.” He has that right. As long as no land was specified, the seller has the ability to choose which land he is going to keep.
Even if the seller did generally specify what piece of land he was giving the buyer, we say that maybe he didn’t really mean the actual piece of land he was giving him in the sale, but maybe was alluding to the value of a piece of land. We say that the seller can say that. If the seller tells his friend, “I’m selling you half of my field in the south,” he does not have to give the southern part of the field to the buyer. Rather, in this case, we say that they divide the land according to its value, and the buyer takes a section worth whatever the piece of land in the south was worth. We evaluate it and say that when the seller said something about his field in the south, he wasn’t talking about the actual field. Rather, he was talking about the monetary value, and that is what he has to give over to his friend in lieu of the southern field he promised him.
If somebody is buying a field, they’re obligated not only to put up fences, but also to provide a piece of land for the fence to rest on. That is between the two halves of the field, and there are other reasons as well. The buyer accepts upon himself that he is going to provide land for building the fence between the two halves of the field. There is also a small trench dug right outside the fence and a smaller one between the trench and the fence. The combination of all these different things—the large trench, the small trench, the wall, everything in this setup—ensures that an animal is not going to get over and cause trouble for the fields.
How much land is needed to build a large trench? The Mishnah answers: six tefachim (handbreadths). Then there is also another type of charitz, another type of trench, a small trench, which is three tefachim. Another tefach needs to be put between the two trenches, so the total amount of land outside the fence that the buyer has to provide is ten tefachim.