Bava Metzia 8B

שמעית מיניה דמר שמואל תרתי: רכוב ומנהיג, חד קני וחד לא קני. ולא ידענא הי מינייהו.

I heard two halakhot from Master Shmuel, one halakha with regard to one who sits in a riding position on an animal, and the other halakha with regard to one who leads an animal. With regard to one case I heard that he thereby acquires the animal, and with regard to the other one I heard that he does not acquire the animal. But I do not know which halakha applies to which of them.

היכי דמי? אילימא רכוב לחודיה ומנהיג לחודיה ⁠– מנהיג לחודיה מי איכא מאן דאמר לא קני? אלא אי איכא למימר דלא קני ⁠– רכוב הוא דאיכא למימר.

The Talmud asks: What are the circumstances? If we say that this is referring to one who sits in a riding position alone and to one who leads alone, is there anyone who says that one who leads an animal alone does not acquire it? Pulling an item, or leading an animal, is a classic mode of acquisition (see Kiddushin 25b). Rather, if there is a case where it could be said that one does not acquire the animal, it is obviously in the case of one who sits in a riding position that it could be said. Therefore, why was Rav Yehuda uncertain?

אלא רכוב במקום מנהיג איבעיא ליה. מאי: רכוב עדיף ⁠– דהא תפיס בה, או דלמא מנהיג עדיף ⁠– דאזלא מחמתיה?

The Talmud answers: Rather, his dilemma was with regard to a case where one sits in a riding position on the animal while another leads it. What is the halakha? Which of them acquires the animal? Does the one sitting in a riding position on the animal take precedence, as the animal is in his grasp, since his legs are grasping the sides of the animal, or perhaps the one leading the animal takes precedence, as it walks because of him?