Bava Metzia 9A

במדה זאת קנו. רבי יהודה אומר: לעולם לא קנה עד שתהא משיכה בגמל והנהגה בחמור.

they have both acquired the animal in that manner. R' Yehuda says: Actually, one acquires an animal only through pulling in the case of a camel or driving in the case of a donkey, as that is the manner in which they are normally directed.

קתני מיהת: או שהיה אחד מושך ואחד מנהיג, מושך ומנהיג ⁠– אין. אבל רכוב לא!

In any event, it is taught in the baraita: Or one who was pulling and one who was driving, which indicates that pulling and driving are indeed effective modes of acquisition, but sitting in a riding position on an animal is not.

הוא הדין דאפילו רכוב, והא דקתני מושך ומנהיג ⁠– לאפוקי מדרבי יהודה דאמר: עד שתהא משיכה בגמל והנהגה בחמור, קמשמע לן דאפילו איפכא נמי קני.

The Talmud rejects this inference: The same is true with regard to even sitting in a riding position on an animal; it is an effective mode of acquisition. And the reason that the baraita teaches specifically the modes of pulling and driving is only to exclude the opinion of R' Yehuda, who says that one acquires an animal only through pulling in the case of a camel or driving in the case of a donkey. Therefore, the first tanna teaches us that even in the opposite manner, i.e., pulling a donkey or driving a camel, one acquires the animal.

אי הכי, ליערבינהו ולתנינהו: שנים שהיו מושכין ומנהיגין בין בגמל בין בחמור!

The Talmud asks: If that is so, then let the first tanna combine the cases and teach them as follows: With regard to two people who were pulling or driving either a camel or a donkey, they each acquire the respective animal. The fact that this wording is not used indicates that the first tanna does not entirely disagree with R' Yehuda.

איכא חד צד דלא קני: איכא דאמרי משיכה בחמור, ואיכא דאמרי הנהגה בגמל.

The Talmud modifies its response: There is one manner of acquisition by which the first tanna concedes to R' Yehuda that one does not acquire the animal if one employs it, and it is unclear what manner that is. Some say that by pulling a donkey one does not acquire it, as donkeys tend to not move at all when being pulled, and some say that by driving a camel one does not acquire it, as that is not the common way to move it.