GEMARA: Shmuel’s father and Levi taught: A partner does not have the ability to establish the presumption of ownership of property in his possession, and, all the more so, this inability applies to a craftsman as well. But Shmuel teaches: A craftsman does not have the ability to establish the presumption of ownership of property in his possession, but a partner does have the ability to establish the presumption of ownership. The Gemara comments: And Shmuel follows his line of reasoning, as Shmuel says: Partners establish the presumption of ownership with regard to the property of each other, and they testify for each other and become paid bailees of their joint property with regard to each other. In terms of these issues, Shmuel considers partners to be independent parties.

Rabbi Abba raises a contradiction to Rav Yehuda in the cave of Rav Zakkai’s house: Did Shmuel actually say that a partner has the ability to establish the presumption of ownership? But doesn’t Shmuel say: A partner is considered as one who enters the field with permission, such as a sharecropper? Isn’t that to say that a partner does not have the ability to establish the presumption of ownership? The Gemara answers: It is not difficult. This is referring to where he enters all of the field, and that is referring to where he enters half of the field.

The Gemara explains: Some say it in this manner and some say it in that manner. On the one hand, it is possible to explain that if he entered half of the field he establishes the presumption of ownership with regard to that half, but if he entered the entire field he is merely acting as a partner. On the other hand, one could explain that entering half of the field does not establish the presumption of ownership at all, while entering the entire field does establish it.

Ravina stated a different resolution to the contradiction: Both this and that are referring to a case where he enters the entire field, and it is not difficult. This is referring to a case where the field is of sufficient area to be subject to the halakha of division. In this case, his being in possession of the other half of the field as well, which belonged to his partner, establishes the presumption of ownership. That is referring to a case where the field is not of sufficient area to be subject to the halakha of division. Since the property will not be divided but will remain co-owned, he is merely possessing it as a partner and does not establish the presumption of ownership.

§ The Gemara addresses the matter itself. Shmuel says: A partner is considered as one who enters the field with permission. What is this teaching us, that there is no the presumption of ownership in the context of partnership? If so, let him say explicitly: A partner does not have the ability to establish the presumption of ownership of property in his possession.

Rav Naḥman says that Rabba bar Avuh says: Shmuel’s intent was to state that a partner who proactively works to improve their mutual property collects the enhancement that reaches shoulders, i.e., when the produce that grew due to the efforts of the partner is fully grown and ripened and can be harvested and carried upon one’s shoulders. He is not considered as one who entered another’s field without permission and improved it, who collects only for his expenditures. This is the halakha if he planted trees in a field that is not commonly used for planting trees, just as it is if he planted in a field that is commonly used for planting trees.

The Gemara continues its discussion of Shmuel’s statement: And testify for each other. A partner may join another witness in testifying with regard to the fact that his partner owns a share of their field in order to counter the claim of a one who claims ownership of the field, and his testimony is not disqualified due to being biased.