Eruvin 90B

דהא איכא מחיצתא. ושמואל אמר: אין מטלטלין בה אלא בארבע אמות ⁠— מחיצות להבריח מים עשויות.

as there are partitions. And Shmuel said: One may move an object in it only within 4 cubits, as the partitions of the ship are not considered full-fledged partitions; they are erected only to keep water out, not to render it a residence.

אמר ליה רב חייא בר יוסף לשמואל: הילכתא כוותך או הילכתא כרב? אמר ליה: הילכתא כרב.

Rav Ḥiyya bar Yosef said to Shmuel: Is the halakha in accordance with your opinion or is the halakha in accordance with the opinion of Rav? Shmuel said to him: The halakha is in accordance with the opinion of Rav, as his rationale is more convincing.

אמר רב גידל אמר רב חייא בר יוסף: ומודה רב שאם כפאה על פיה, שאין מטלטלין בה אלא בארבע אמות. כפאה, למאי? אילימא לדור תחתיה, מאי שנא מגג יחידי?

Rav Giddel said that Rav Ḥiyya bar Yosef said: And Rav concedes that if one overturned the ship onto its mouth, and it is more than 10 handbreadths high, that one may move an object on it only within 4 cubits. The Talmud asks: For what purpose was the ship overturned? If you say it was overturned so that one may reside beneath it, what is the difference between it and an isolated roof? The legal status of the overturned ship should in every sense be that of a house, and therefore it should be permitted to carry throughout the entire ship.

אלא שכפאה לזופתה.

Rather, it must be that he overturned it to tar it, i.e., to add a fresh coat to its underside. In that case, the boat certainly does not serve as a residence, and its sides are not considered full-fledged partitions.

רב אשי מתני לה אספינה, ורב אחא בריה דרבא מתני לה אאכסדרא. דאיתמר, אכסדרה בבקעה. רב אמר: מותר לטלטל בכולה, ושמואל אמר: אין מטלטלין בה אלא בארבע.

Rav Ashi teaches Shmuel’s acceptance of Rav’s opposing view (Ritva) with regard to a ship, as stated above; and Rav Aḥa, son of Rava, teaches it with regard to a portico, as it was stated that amora’im disagreed with regard to a portico located in a field. A portico has a roof and either incomplete walls or no walls. Consequently, in the case of a portico located in a valley, which is a karmelit, it remains to be determined whether or not it is permitted to carry in it. Rav said: It is permitted to move an object throughout the entire portico, as it is a private domain. And Shmuel said: One may move an object in it only within 4 cubits.