Avodah Zarah Daf 72 עבודה זרח דַף 72

Once, a man told someone: אי מזביננא לה להא ארעא לך מזביננא לה – “If I ever sell this field, I will sell it to you,” (and made a kinyan on this guarantee). Later, he sold it to someone else. Rav Yosef said: קנה קמא – the first one acquires the field, because of their agreement. Abaye objected: והא לא פסק – but he did not set a price for the sale, so the guarantee is ineffective (i.e., the buyer was not fully committed, since the seller can ask an exorbitant price)!? This argument is supported by a Baraisa teaching that a buyer does not acquire merchandise measured and placed in his chatzeir if a price was not set. In another incident, a man told someone, “If I ever sell this field, מזביננא לך במאה זוזי – I will sell it to you for one hundred maneh.” Later, he sold it to someone else for hundred twenty maneh, and Rav Kahana said the first one acquires it (since a price was set). However, Rav Yaakov of נהר פקוד objected: האי זוזי אנסוהו – the [additional] zuzi “forced” this man to sell his field! Meaning, he only committed to sell it to the first person if he would decide to sell it for its value; here, he only agreed to sell it because of the high price he was offered. The halachah follows this opinion.

A Mishnah teaches that נצוק – a midair stream of liquid, קטפרס – liquid running down a slope, and משקה טופח – liquid sufficient to moisten that which touches it, are not considered a connection between two liquids regarding tumah (i.e., a tamei person touching the liquid in the lower container would not be metamei liquid in the upper container), nor for taharah (i.e., an upper mikveh containing less than forty סאה does not become valid via this connection to a lower valid mikveh). Rav Huna taught that נצוק וקטפרס ומשקה טופח are considered a חיבור – connection regarding יין נסך. Therefore, if one pours wine into יין נסך, even the wine in the upper container is prohibited as יין נסך. Several attempts to prove this ruling are deflected. Later, the Gemara reports that Rav Chisda advised Jewish wine sellers to pour for idolators in spurts, to avoid prohibiting their own wine, because he held נצוק חיבור regarding יין נסך.

The Gemara attempts to prove that נצוק is a חיבור from a Baraisa, which states that if one pours wine from a barrel into a wine pit, קילוח היורד משפת חבית למטה אסור – the flow descending from the barrel’s edge and downward is forbidden. This proves that the midair stream is connected to the pit below, which contains יין נסך!? Rav Sheishess answered that the Baraisa is בעובד כוכבים המערה דאתי מכחו – with an idolator who is pouring the wine, because it is moving through [the עכו"ם’s] force, which prohibits the wine (not because of יין נסך in the pit). The Gemara asks that if so, the wine in the barrel should also be prohibited, since that wine was also moved by the עכו"ם!? In answers: כח דעובד כוכבים מדרבנן הוא דאסיר – wine moved by an עכו"ם’s force is prohibited only Rabbinically. ההוא דנפק לבראי גזרו ביה רבנן – Therefore, regarding wine which went outside the barrel, the Rabbis decreed to prohibit it, ההוא דלגואי לא גזרו ביה רבנן – but regarding that which remained inside the barrel, the Rabbis did not decree to prohibit it.