No, this ruling is necessary to teach that the room behind the house is excluded from the sale of the house even if the seller delineated the boundaries of the house for the buyer in the bill of sale by listing places outside the room, e.g., noting the houses that border the property being sold. Even though this might suggest that the room is included in the sale, the mishna teaches that it is not.

This is in accordance with the opinion of Rav Naḥman, as Rav Naḥman says that Rabba bar Avuh says: With regard to one who sells a residence to another in a large building [bira] containing several residences, even if he delineates for him the external boundaries of the large building, he did not sell him the entire building, but rather he enlarged upon the boundaries for him. That is, the seller did not mean to delineate the precise borders of what he was selling; rather, he delineated the boundaries in a broad manner, giving the general location of the specific residence subject to the transaction.

With regard to Rav Naḥman’s statement, the Gemara inquires: What are the circumstances of the case? If we say that this is referring to a place where they call a residence a residence, and a building a building, and they always differentiate between the two terms, it is obvious that he did not intend to sell him the entire building but merely enlarged upon the boundaries for him, as he sold him a residence and did not sell him a large building. Rather, explain that this is referring to a place where they also call a building a residence. But in that case, why not say that the seller sold him the entire building, since he delineated the external boundaries of the large building?

The Gemara answers: No, Rav Naḥman’s ruling is necessary in a place where most of the people call a residence a residence, and a building they call a building, but there are also some people who call a building a residence. Lest you say that since the seller delineated the building’s external boundaries, this indicates that he meant to sell him the entire building, Rav Naḥman teaches us that this is not so. As, if the seller intended to sell him the entire building, he would have written in the bill of sale: And I have not withheld anything for myself in this sale, but if he did not write this clause, conclude from it that the seller withheld something for himself and did not mean to sell everything located within the delineated boundaries.

And in a similar fashion, Rav Naḥman says that Rabba bar Avuh says: With regard to one who sells a field to another in a large expanse of fields, even if he delineates for him the external boundaries of the large expanse of fields he did not sell him the entire expanse of fields; rather, he enlarged upon the boundaries for him. That is, the seller did not mean to delineate the precise borders of what was being sold; rather, he delineated the boundaries in a broad manner, giving the general location of the particular field he was selling.

The Gemara inquires: What are the circumstances of the case? If we say that this is referring to a place where they call a field a field, and an expanse of fields an expanse of fields, and always differentiate between the two terms, it is obvious the he did not intend to sell him the entire expanse of fields, as he sold him a field and did not sell him an expanse of fields. Rather, explain that this is referring to a place where they also call an expanse of fields a field. But in that case, why not say that the seller sold him the entire expanse of fields, since he delineated the external boundaries of the expanse of fields?

The Gemara answers: No, Rav Naḥman’s ruling is necessary in a place where there are some people who call a field a field, and an expanse of fields they call an expanse of fields, but there are also some people who call an expanse of fields a field. Lest you say that since the seller delineated the expanse’s external boundaries, this indicates that he meant to sell him the entire expanse, Rav Naḥman teaches us that this is not so. As, if the seller intended to sell him the entire expanse, he would have written for him in the bill of sale: And I have not withheld anything for myself in this sale, but since he did not write this clause for him, conclude from it that the seller withheld something for himself and did not mean to sell everything located within the delineated boundaries.

The Gemara notes: And it was necessary for Rav Naḥman to teach the halakha in both cases, even though the two rulings appear to be the same. As had he taught us the halakha only in the case of the residence, that he did not sell him the entire building even if he delineated the building’s external boundaries, I might have said that this is due to the fact that this, the residence, has a discrete use, separate from that of the rest of the building, and that, the building, has a discrete use. But as for an expanse of fields, all of which has a single use, since it can be sown with grain in its entirety, say that the seller sold him the entire expanse.

And had Rav Naḥman taught us the halakha only in the case of an expanse of fields, that he did not sell him the entire expanse even if he delineated its external boundaries, I might have said that this is due to the fact that the seller had no way to delineate the particular field’s boundaries, since all of the fields are similar, and they all belong to the seller. But as for a residence, with regard to which the seller had a way to delineate its borders, through the use of descriptive terms that would isolate it from the rest of the building, but he did not delineate them, I might say that he sold him the entire building. Therefore, it was necessary to mention both cases explicitly.

The Gemara asks: In accordance with whose opinion is that which Rav Mari, son of the daughter of Shmuel, said in the name of Abaye: One who sells something to another must write for him in the bill of sale: I have not withheld anything for myself in this sale. In accordance with whose opinion is that? It is in accordance with the opinion of Rav Naḥman, who says that Rabba bar Avuh says that even when the seller delineates the boundaries of what he is selling, he does not necessarily mean to sell everything included within those boundaries. Inserting this clause in the bill of sale removes uncertainties that could lead to conflict.

The Gemara relates: There was a certain man who said to another: I am selling you land of the house of Ḥiyya, but there were two plots of land that were called that of the house of Ḥiyya, and the Sages deliberated as to whether both were included in this sale or only one. Rav Ashi said: He said to him that he was selling him one plot of land, and he did not say to him that he was selling him two plots of land, as he employed a singular term. Therefore, only one is included in the sale.

And if he said to him: I am selling you fields, without specifying how many, the minimum number of fields that would justify being called fields in the plural is two, and therefore the seller has to give the buyer only two of his fields, even if he owns many fields. And if he said to him: I am selling you all of my fields, what he means is that he is selling him all the fields that he owns, excluding his orchards [bustanei] and vineyards. And if he said to him: I am selling you my landed property, what he means is that he is selling him even his orchards and vineyards, but excluding his houses and Canaanite slaves.