דרך עליו חייב התם לא נח הכא נח:
via the airspace above it, i.e., he raised the object more than ten handbreadths above the ground of the public domain, which is an exempt domain, still he is liable for carrying in the public domain. On the other hand, in the Tosefta it says that if the object passed through an exempt domain, he is exempt by Torah law from punishment for passing it from domain to domain. The Gemara rejects that refutation as there is room to distinguish between the cases: There, in the halakha stated by Rava, the object did not come to rest in an exempt domain; it merely passed through its airspace. However, here, when transferred via the threshold, the object came to rest in an exempt domain, and as a result, the act of carrying out was divided into two separate actions, neither of which involves a Torah prohibition.
אחרים אומרים אסקופה משמשת שתי רשויות בזמן שהפתח פתוח כלפנים פתח נעול כלחוץ
Later in the Tosefta, Aḥerim say: Depending on the circumstances, a threshold serves two domains: When the entrance is open, the threshold is subsumed within the house and it is considered to be a private domain like the inside of the house. And when the entrance is locked, the threshold is not subsumed within the house, and it is considered to be a public domain like the outside.
ואף על גב דלית ליה לחי והאמר רב חמא בר גוריא אמר רב תוך הפתח צריך לחי אחר להתירו
The Gemara wonders: When the entrance is open the threshold is considered to be like a private domain, and is this so even though it does not have a post on its side? Didn’t Rav Ḥama bar Gurya say that Rav said: The opening in the wall, i.e., the doorway, requires another post in order to permit carrying there? A symbolic partition must be established at the side of the opening for that doorway to be considered closed and render carrying within it permissible like a full-fledged private domain. In the Tosefta, no mention was made of the need for a post of that kind.
וכי תימא דלית ביה ארבעה על ארבעה והאמר רב חמא בר גוריא אמר רב תוך הפתח אף על פי שאין בו ארבעה על ארבעה צריך לחי אחר להתירו
And if you say that the Tosefta is referring to a threshold that does not have an area of four by four handbreadths, which is not considered an independent area and therefore does not require a post, didn’t Rav Ḥama bar Gurya say that Rav said explicitly: The opening, even though it does not have an area of four by four handbreadths, requires another post in order to permit carrying there?
אמר רב יהודה אמר רב הכא באיסקופת מבוי עסקינן חציו מקורה וחציו שאינו מקורה וקירויו כלפי פנים פתח פתוח כלפנים פתח נעול כלחוץ
Rav Yehuda said that Rav said: Here we are dealing with the threshold of an alleyway open to the public domain on only one side. Although, by Torah law, it is considered a private domain, the Sages required him to establish a fourth symbolic partition on the side open to the public domain. This alleyway was covered, and this covering extended to part of the threshold in a manner that half of it is covered and half of it is not covered, and the covering is over the part of the threshold toward the inside. In that case, if the entrance is open, its legal status is like that of the inside, as it is considered as if there were a partition extending from the edge of the roofing above to below, based on the halakhic principle: Lower the partition. The opening of the alleyway is thereby sealed, rendering it a private domain. However, when the entrance is locked, it is no longer possible to consider the covering as a partition, and therefore the part of the threshold that is beyond the locked door of the alleyway is considered like the outside, i.e., like a public domain.
רב אשי אמר לעולם באיסקופת בית עסקינן וכגון שקירה בשתי קורות שאין בזו ארבעה ואין בזו ארבעה ואין בין זו לזו שלשה ודלת באמצע פתח פתוח כלפנים פתח נעול כלחוץ:
Rav Ashi said: Actually, we can say that we are dealing with the threshold of a house, and in a special circumstance, a case where he covered the threshold with two beams. Furthermore, neither this beam is four handbreadths wide, nor is that beam four handbreadths wide, and there is not a gap of three handbreadths between this one and that one, and there is a door between the two beams. In this case, when the entrance is open, since there is a space of less than three handbreadths between the beams and, based on the principle of lavud, any space less than three handbreadths is considered non-existent, the two beams are considered to be one wide beam. It is considered as if there were a partition extending from the edge of the roofing above to below, based on the halakhic principle: Lower the partition. The threshold is thereby sealed and considered a full-fledged private domain like the inside. However, when the entrance is locked, the two beams do not join together to become one anymore. Since the door creates a separation between them and the outer beam is less than four handbreadths wide, it is not considered a roof from which a partition extends to the ground, and the area under this beam is considered to be a public domain like the outside.
ואם היתה איסקופה גבוהה עשרה ורחבה ארבעה הרי זו רשות לעצמה מסייע ליה לרב יצחק בר אבדימי דאמר רב יצחק בר אבדימי אומר היה רבי מאיר כל מקום שאתה מוצא שתי רשויות והן רשות אחת כגון עמוד ברשות היחיד גבוה עשרה ורחב ארבעה אסור לכתף עליו גזירה משום תל ברשות הרבים:
The Sage also said in the Tosefta that if the threshold was ten handbreadths high and four by four handbreadths wide, it is an independent domain, even if it was inside a private domain. The Gemara comments: This supports the opinion of Rav Yitzḥak bar Avdimi, as Rav Yitzḥak bar Avdimi said that Rabbi Meir used to say: Any place that you find two domains, i.e., two places, each of which is sufficiently distinct to be an independent domain, and even though they are halakhically one domain, i.e., in a case where a pillar that is ten handbreadths high and four by four wide is standing in the private domain, even though the pillar is a private domain based on its measurements, it is prohibited by rabbinic law to adjust a burden on one’s shoulders upon it and to lift an object from the ground of the private domain and place it atop the pillar, as the pillar is deemed by its measurements to be an independent domain. It is prohibited by a decree issued by the Sages due to a similar situation, the case of a mound of that size in the public domain. In the public domain, lifting an object from the ground and placing it on the mound constitutes a violation of the Torah prohibition of carrying out from the public domain to the private domain. Therefore, the Sages prohibited placing an object on a pillar even in the private domain.