ומנא תימרא דאמרינן כי האי גוונא דתנן בש"א לא ימכור אדם פרה החורשת בשביעית וב"ה מתירין מפני שיכול לשוחטה
Rav Huna added: And from where do you say that in a case like this we say that the animal will be slaughtered, and one is not concerned about placing a stumbling block before the blind, despite the fact that the animal could be used to violate a prohibition? As we learned in a mishna (Shevi’it 5:8) that Beit Shammai say: A person may not sell a cow that plows in the Sabbatical Year, as it is prohibited to plow during the Sabbatical Year and the buyer presumably wants it for this purpose. And Beit Hillel permit selling the cow, since the buyer can slaughter it rather than use it for plowing. This shows that according to Beit Hillel, whose opinion is accepted as halakha, one may assume that an animal will be used for a permitted purpose, rather than for a prohibited action.
אמר רבה מי דמי התם אין אדם מצווה על שביתת בהמתו בשביעית הכא אדם מצווה על שביתת בהמתו בשבת
Rabba said: Are these matters comparable? There, with regard to the Sabbatical Year, a person is not commanded to let his animal rest during the Sabbatical Year, as there is no prohibition against his animal performing labor. Therefore, there is no reason to decree that the sale is prohibited lest he lend, lease, or test the animal. As for the concern that he is misleading the buyer and encouraging him to sin, he may rely on the fact that the buyer probably intends to slaughter the animal. But here, with regard to selling an animal to a gentile, a person is commanded to let his animal rest on Shabbat, and therefore the Sages decreed the sale prohibited in case he comes to lend, lease, or test the animal.
א"ל אביי וכל היכא דאדם מצווה אסור והרי שדה דאדם מצווה על שביתת שדהו בשביעית ותנן בש"א לא ימכור אדם שדה ניר בשביעית וב"ה מתירין מפני שיכול להובירה
Abaye said to Rabba: And does this mean that wherever a person is commanded to allow his possessions to rest it is prohibited to sell an item to one who might use it to perform labor, even if he might also use it for an innocent purpose? But there is the case of a field, as a person is commanded to let his field rest during the Sabbatical Year, and yet we learned in a baraita that Beit Shammai say: A person may not sell a plowed field during the Sabbatical Year, as it is presumed that the buyer will sow it, and Beit Hillel permit this sale, since the buyer can let it lie fallow during the Sabbatical Year. In this case, although one is commanded to let his field rest during the Sabbatical Year, he may still sell it under the assumption that the buyer will use the field in a permitted manner.
מתקיף לה רב אשי וכל היכא דאין אדם מצווה שרי והרי כלים דאין אדם מצווה על שביתת כלים בשביעית ותנן אלו הן כלים שאין אדם רשאי למוכרן בשביעית המחרישה וכל כליה העול והמזרה והדקר
Rav Ashi also objects to Rabba’s statement: And conversely, is it true that wherever a person is not commanded to allow his possessions to rest it is permitted to sell the item? But there is the case of vessels, as a person is not commanded to let his vessels rest during the Sabbatical Year, and yet we learned in a mishna (Shevi’it 5:6): These are the implements that a person is not allowed to sell during the Sabbatical Year: The plow and all of its appurtenances, the yoke that is used to hitch the cow to the plow, and the winnowing fork, and the stake.
אלא אמר רב אשי כל היכא דאיכא למיתלא תלינן ואע"ג דמצווה וכל היכא דליכא למיתלי לא תלינן אע"ג דאינו מצווה
Rather, Rav Ashi said: Anywhere that it is possible to assign an innocent motive, one assigns such a motive, and this applies even though one is commanded to allow the item to rest. And anywhere that it is not possible to assign an innocent motive, one does not assign an innocent motive, even though one is not commanded to allow the item to rest.
רבה זבין ההוא חמרא לישראל החשיד למכור לעובד כוכבים א"ל אביי מ"ט עבד מר הכי א"ל אנא לישראל זביני א"ל והא אזיל ומזבין ליה לעובד כוכבים לעובד כוכבים קא מזבין לישראל לא קא מזבין
§ The Gemara relates: Rabba sold a certain donkey to a Jew who was suspected of selling large livestock to a gentile. Abaye said to Rabba: What is the reason that the Master acted in this manner? Rabba said to him: I sold the donkey to a Jew. Abaye said to him: But he will go and sell it to a gentile. Rabba responded: Is the only possibility that he will sell to a gentile, and he will not sell it to a Jew? Since there is no reason to assume that he will sell specifically to a gentile rather than to a Jew, there is no problem in selling to him.
איתיביה מקום שנהגו למכור בהמה דקה לכותים מוכרין שלא למכור אין מוכרין מ"ט אילימא משום דחשידי ארביעה ומי חשידי והתניא אין מעמידין בהמה בפונדקאות של עובדי כוכבים זכרים אצל זכרים ונקבות אצל נקבות ואין צ"ל נקבות אצל זכרים וזכרים אצל נקבות
Abaye raised an objection to Rabba’s opinion from a baraita: In a place where the people were accustomed to sell small livestock to Samaritans, one may sell the animals to them; in a place where the people were not accustomed to sell them one may not sell the animals to them. What is the reason that the sale of small livestock to Samaritans is prohibited? If we say that it is because Samaritans are suspected of engaging in bestiality, are they suspected of this practice? But isn’t it taught in a baraita: One may not keep an animal in the inns of gentiles. Male animals may not be placed with men, as they are suspected of engaging in bestiality, and female animals may not be left with women, despite the fact that there is no concern that they may engage in bestiality. And needless to say, it is prohibited to leave female animals with men, and male animals with women.
ואין מוסרין בהמה לרועה שלהן ואין מייחדין עמהם ואין מוסרין להם תינוק ללמדו ספר וללמדו אומנות אבל מעמידין בהמה בפונדקאות של כותים זכרים אצל נקבות ונקבות אצל זכרים ואין צ"ל זכרים אצל זכרים ונקבות אצל נקבות
The baraita continues: And one may not entrust an animal to a gentile shepherd, and one may not seclude oneself with gentiles, due to the danger that this entails. And one may not entrust a child to them to teach him how to read books or to teach him a craft. But one may keep an animal in the inns of Samaritans, as they are not suspected of violating a Torah prohibition and engaging in bestiality. Male animals may be placed with women and female animals may be left with men, and needless to say, it is permitted to leave male animals with men and female animals with women.
ומוסרין בהמה לרועה שלהן ומייחדין עמהם ומוסרין להם תינוק ללמדו ספר וללמדו אומנות אלמא לא חשידי
The baraita concludes: And one may entrust an animal to a Samaritan shepherd, and one may seclude oneself with Samaritans, and one may entrust a child to them to teach him how to read books and to teach him a craft. The Gemara infers from the baraita: Evidently, Samaritans are not suspected of engaging in bestiality, yet livestock may not be sold to them, as they are suspected of selling it to gentiles.
ועוד תניא אין מוכרין להם לא זיין ולא כלי זיין ואין משחיזין להן את הזיין ואין מוכרין להן לא סדן ולא קולרין ולא כבלים ולא שלשלאות של ברזל אחד עובד כוכבים ואחד כותי
And furthermore, it is taught in a baraita: One may not sell weapons to gentiles or the auxiliary equipment of weapons, and one may not sharpen weapons for them. And one may not sell them stocks used for fastening the feet of prisoners, or iron neck chains [kolarin], or foot chains, or iron chains. This prohibition applies equally to both a gentile and a Samaritan.
מ"ט אי נימא דחשידי אשפיכות דמים ומי חשידי האמרת ומייחדין עמהן אלא משום דאתי לזבונה לעובד כוכבים
Abaye analyzes this baraita: What is the reason for the prohibition against selling these items to Samaritans? If we say that they are suspected of bloodshed, that is difficult: But are they suspected of this? Didn’t you say that one may seclude oneself with them, which indicates that they are not suspected of bloodshed? Rather, it is prohibited to sell these items to Samaritans because they will come to sell them to a gentile. According to this reasoning, it should likewise be prohibited to sell a donkey to a Jew who is suspected of selling animals to gentiles.
וכי תימא כותי לא עביד תשובה ישראל עביד תשובה והאמר רב נחמן אמר רבה בר אבוה כדרך שאמרו אסור למכור לעובד כוכבים כך אסור למכור לישראל החשוד למכור לעובד כוכבים רהיט בתריה תלתא פרסי וא"ד פרסא בחלא ולא אדרכיה
And if you would say that there is a difference between a Jew and a Samaritan, as a Samaritan will likely not repent and will sell to a gentile, whereas a Jew will likely repent and not sell these items, this reasoning is incorrect. But doesn’t Rav Naḥman say explicitly that Rabba bar Avuh says: Just as the Sages said that it is prohibited to sell to a gentile, so too it is prohibited to sell to a Jew who is suspected of selling to a gentile? When Rabba heard this and realized that Abaye was correct, he ran three parasangs after the buyer who purchased his donkey to revoke the sale, as the Jew was suspected of selling to gentiles; and some say that he ran one parasang through sand. But he did not succeed in overtaking him.
א"ר דימי בר אבא כדרך שאסור למכור לעובד כוכבים אסור למכור ללסטים ישראל ה"ד אי דחשיד דקטיל פשיטא היינו עובד כוכבים
Apropos the baraita that discusses the prohibition against selling weapons, the Gemara relates that Rav Dimi bar Abba says: Just as it is prohibited to sell to a gentile, it is prohibited to sell to an armed bandit who is a Jew. The Gemara clarifies: What are the circumstances of this prohibition? If the thief is suspected of killing, isn’t it obvious that it is prohibited? After all, he is the same as a gentile. Providing a Jew who might kill with weapons is no different from giving a weapon to a gentile, as in both cases one violates the prohibition: Do not place a stumbling block before the blind.
ואי דלא קטיל אמאי לא לעולם דלא קטיל והב"ע במשמוטא דזימנין דעביד לאצולי נפשיה
And if he is a bandit who does not kill, why not sell to him? The Gemara answers: Actually, Rav Dimi bar Abba is referring to a bandit who does not kill, and here we are dealing with a bandit who steals, as sometimes he makes use of his weapon to save himself when he is caught. Consequently, it is prohibited to sell him weapons in case he kills with them in self-defense.
תנו רבנן אין מוכרין להן תריסין וי"א מוכרין להן תריסין מ"ט אילימא משום דמגנו עלייהו אי הכי אפילו חיטי ושערי נמי לא אמר רב
§ The Sages taught: One may not sell shields [terisin] to gentiles, despite the fact that they are used for protection, not to attack others. And some say: One may sell shields to them. The Gemara asks: What is the reason behind the opinion that prohibits selling shields to gentiles? If we say it is because they protect them in wartime, if so, then even wheat and barley should not be sold to them. Rav said: