Avodah Zarah 15b:3עבודה זרה ט״ו ב:ג׳
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.
Rashi on Avodah Zarah 15b:3:1רש"י על עבודה זרה ט״ו ב:ג׳:א׳
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Tosafot on Avodah Zarah 15b:2:1תוספות על עבודה זרה ט״ו ב:ב׳:א׳
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