אַמַּאי שְׁמִירָה בִּבְעָלִים הִיא אָמַר רַב פָּפָּא דְּאָמַר לֵיהּ שְׁמוֹר לִי הַיּוֹם וַאֲנִי אֶשְׁמוֹר לְךָ לְמָחָר: The Gemara asks: Why are they liable as paid bailees? Isn’t it a case of safeguarding accompanied by employment of the owner? Since both partners are safeguarding each other’s property, they are both employed by each other, and they should therefore be exempt from the obligations of safeguarding. Rav Pappa said: Shmuel is referring to a case where he says to his partner: Safeguard for me today, and I will safeguard for you tomorrow. In this circumstance, they are each the sole bailee at any given moment, and they do not receive the exemption from bailee payments for being employed by the owner.
תָּנוּ רַבָּנַן מָכַר לוֹ בַּיִת מָכַר לוֹ שָׂדֶה אֵין מֵעִיד לוֹ עָלֶיהָ מִפְּנֵי שֶׁאַחְרָיוּתוֹ עָלָיו מָכַר לוֹ פָּרָה מָכַר לוֹ טַלִּית מֵעִיד לוֹ עָלֶיהָ מִפְּנֵי שֶׁאֵין אַחְרָיוּתוֹ עָלָיו מַאי שְׁנָא רֵישָׁא וּמַאי שְׁנָא סֵיפָא § The Sages taught: If one sold a house to another, or if he sold a field to him, he cannot testify about it for the buyer against a claimant because the financial responsibility to compensate the buyer for it is upon him, and his testimony is biased. By contrast, if he sold a cow to him, or if he sold a cloak to him, he can testify about it for the buyer because the financial responsibility to compensate the buyer for it is not upon him. The Gemara asks: What is different in the first clause that he cannot testify and what is different in the latter clause that he can? Why would one assume that in the first case he does bear responsibility, but not in the second?
אָמַר רַב שֵׁשֶׁת רֵישָׁא בִּרְאוּבֵן שֶׁגָּזַל שָׂדֶה מִשִּׁמְעוֹן וּמְכָרָהּ לְלֵוִי וַאֲתָא יְהוּדָה וְקָא מְעַרְעֵר דְּלָא לֵיזִיל שִׁמְעוֹן לַאסְהֵיד לֵיהּ לְלֵוִי דְּנִיחָא לֵיהּ דְּהָדְרָא Rav Sheshet said: The first clause is stated with regard to the case of Reuven, who robbed Shimon of a field and sold it to Levi, and then Yehuda comes and contests Levi’s ownership, stating that it was actually his. The baraita teaches that Shimon cannot go to court to testify for Levi, because it is preferable for Shimon that the field be returned to Levi, so that he can later collect it from him.
וְכֵיוָן דְּאַסְהֵיד לֵיהּ דְּלֵוִי הוּא הֵיכִי מָצֵי מַפֵּיק לַהּ מִינֵּיהּ דְּאָמַר יָדַעְנָא דְּהַאי אַרְעָא דְּלָאו דִּיהוּדָה הִיא וּבְהָהוּא זְכוּתָא דְּקָא מַפֵּיק לַהּ מִלֵּוִי לַיפְּקַהּ מִיהוּדָה The Gemara asks: But once he testified that the field is Levi’s, how is he able to later remove it from his possession? The Gemara answers: This is referring to a case where Shimon says in his testimony: I know that this land is not Yehuda’s, but he did not explicitly testify that it belonged to Levi. He is therefore able to later claim it is his and not Levi’s. The Gemara asks: But why should he testify that it does not belong to Yehuda? With that same right by which he removes the land from the possession of Levi, let him remove it from the possession of Yehuda. It is not to his advantage to lie in order to establish it in the possession of Levi, and his testimony should not be considered biased.
דְּאָמַר הַשֵּׁנִי נוֹחַ לִי הָרִאשׁוֹן קָשֶׁה הֵימֶנּוּ The Gemara answers: Because Shimon says to himself: The second person is amenable to me, while the first is more difficult than he is, i.e., I prefer to litigate with Levi rather than with Yehuda.
וְאִי בָּעֵית אֵימָא כְּגוֹן דְּאִית לֵיהּ סָהֲדֵי לְמָר וְאִית לֵיהּ סָהֲדֵי לְמָר וַאֲמוּר רַבָּנַן אַרְעָא הֵיכָא דְּקַיְימָא תֵּיקוּם And if you wish, say instead: It is referring to a case where this Master, Shimon, has witnesses attesting to his ownership, and that Master, Yehuda, also has witnesses attesting to his ownership, and the Sages said that under such circumstances the land should remain where it is. That is to say, it should remain with the one currently in possession. If Yehuda were to be awarded the land, Shimon would not be able to remove the land from his possession despite having witnesses to support his claim, as Yehuda also has witnesses supporting his claim and would be in possession of the land. As a result of Shimon’s testimony, the land will be awarded to Levi, who has possession as a result of his purchase from Reuven. Then Shimon will be able to remove the land from Levi’s possession by proving that Reuven stole it from him. Therefore, Shimon’s testimony is biased.