Talmud - Bava Metzia 9b בבא מציעא ט׳ ב׳

And if he rides it in the public domain, he acquires it, as people commonly ride animals in the city’s public domain. And if he is an important person, who always rides his animal rather than leading it, he acquires it even in an alleyway. And if the buyer is a woman, she acquires the animal, as women do not normally lead animals. And if the buyer is a detestable person, who rides even where other people do not, he too acquires the animal.

§ Rabbi Elazar raises a dilemma: With regard to one who says to another, to whom he wishes to sell vessels: Pull this animal in order to acquire the vessels that are upon it, what is the halakha? Can the buyer acquire the vessels by pulling the animal?

Before discussing the dilemma, the Gemara clarifies the issue. If the vendor merely says: In order that you will acquire the vessels, how can the buyer acquire them? Did he say to him in the imperative: Acquire the vessels? Without the seller’s explicitly instructing the buyer to acquire the vessels, the buyer cannot acquire them. Rather, Rabbi Elazar’s dilemma is with regard to a case where the seller says to the buyer: Pull this animal and thereby acquire the vessels that are upon it. What is the halakha? Is pulling the animal effective in order to acquire the vessels upon it, or not?

Rava said: It is clearly not effective, as even if he said to him: Acquire the animal and acquire the vessels, does the buyer acquire the vessels? Although one can acquire an item by having it placed in his courtyard, and one’s animal is the equivalent of his courtyard, it is considered a mobile courtyard, and a mobile courtyard does not effect acquisition of items that are placed in it.

And if you would say that the animal can function as a courtyard when it is standing still, not walking, while being pulled, isn’t there a principle which states that anything that does not effect acquisition when moving also does not effect acquisition when it is standing or sitting?

The Gemara concludes: And the halakha is that the buyer can acquire vessels by having them placed on the animal’s back only when the animal is bound. In that circumstance, when the buyer acquires the animal it assumes the legal status of his courtyard, and he also acquires the items that are placed upon the animal.

Rav Pappa and Rav Huna, son of Rav Yehoshua, said to Rava: If that is so, in a case where one was sailing on a boat and fish jumped and fell into the boat, is the boat also considered a mobile courtyard, and therefore he does not acquire the fish? Rava said to them: A boat is not considered a mobile courtyard, as the boat itself sits idle, and it is the water that moves it.

Ravina said to Rav Ashi: If that is so, that one does not acquire items that are placed in his mobile courtyard, then if a woman was walking in the public domain and her husband threw a bill of divorce into her lap, i.e., onto her person, or into her basket that she was carrying on her head, here too, is she not divorced because the basket was moving? Rav Ashi said to him: Her basket is not considered a mobile courtyard, as it sits idle, and it is she who walks beneath it.

MISHNA: If one was riding on an animal and saw a found item, and said to another person who was walking beside him: Give it to me, if the pedestrian took it and said: I have acquired it for myself, he has acquired it by means of lifting it, even though he did not see it first. But if, after giving it to the one riding the animal, he said: I acquired it for myself at the outset, he has said nothing and the rider keeps the item.

GEMARA: We learned in a mishna there (Pe’a 4:9): With regard to one who gleaned the produce in the corner of the field, which is given to the poor [pe’a], and said: This produce is for so-and-so, a poor person, Rabbi Eliezer says: He thereby acquired it on the poor person’s behalf. And the Rabbis say: He did not acquire it for the poor person; rather, he should give it to the first poor person that he encounters.

Ulla said that Rabbi Yehoshua ben Levi said: This dispute is in a case where the pe’a was gleaned by a rich person, who is not entitled to take the pe’a for himself, on behalf of a poor person.

As Rabbi Eliezer holds that since [miggo], if he so desires, he can renounce ownership of his property and he would then be poor, and the pe’a would then be suitable for him, now too, it is considered potentially suitable for him even though he is wealthy. And since [miggo] he can acquire it for himself, he can acquire it on behalf of another poor person as well. And the Rabbis hold that we say miggo once, but we do not say miggo twice. Therefore, a wealthy person cannot acquire pe’a for a poor person.

But in a case where the pe’a was gleaned by a poor person on behalf of another poor person, everyone agrees that he acquires it on behalf of the other person, as since [miggo] he can acquire it for himself, he can acquire it on behalf of another person as well.

Rav Naḥman said to Ulla: But shouldn’t the Master say that the dispute is even in a case where the pe’a was gleaned by a poor person on behalf of another poor person? This can be proven from the mishna, as everyone is considered like poor people with regard to a found item, i.e., everyone has the right to acquire a found item just as a poor person is entitled to glean pe’a, and we learned in the mishna: If one was riding on an animal and saw a found item, and said to another person: Give it to me, if the pedestrian took it and said: I have acquired it for myself, he has acquired it.

Granted, if you say the dispute pertains to a case where the pe’a was gleaned by a poor person on behalf of a poor person,

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

BavaMetzia 9b explores acquiring an animal through riding versus leading it, then debates whether pulling an animal also transfers ownership of vessels placed on it.