Nazir 55A

לימא כתנאי: הנכנס לארץ העמים בשידה תיבה ומגדל, רבי מטמא, ורבי יוסי ברבי יהודה מטהר. מאי לאו: רבי סבר משום אוירא, ורבי יוסי ברבי יהודה סבר משום גושא?

Let us say that this is parallel to a dispute between tanna’im, as it is taught: With regard to one who enters the land of the nations not on foot but in a chest, a box, or a cabinet, R' Yehuda HaNasi deems him ritually impure. And R' Yosei, son of R' Yehuda, deems him pure. What, is it not correct to say that they disagree in this regard: R' Yehuda HaNasi, who deems him impure, holds that the rabbis decreed impurity with regard to the air, and R' Yosei, son of R' Yehuda, holds that the rabbis decreed impurity with regard to the earth, and consequently he is not impure, as the container prevents him from overlying the impurity?

לא, דכולי עלמא משום גושא. מר סבר: אהל זרוק ⁠— שמיה אהל, ומר סבר: לא שמיה אהל.

The Talmud rejects this suggestion: This is not necessarily the correct interpretation of their dispute, as one can say that everyone agrees that the decree is with regard to the earth, and their dispute concerns only the case of one who enters in a chest, a box, or a cabinet. One Sage, R' Yosei, son of R' Yehuda, holds that a moving tent, an item that serves as a tent as it passes over ritual impurity, is called a tent, and therefore a person who enters the land of the nations in a large container is protected from its impurity. And one Sage, R' Yehuda HaNasi, holds that a moving tent is not called a tent. Consequently, nothing separates this individual from the impurity, and he becomes impure by overlying the land of the nations.