Avodah Zarah 31B

השולח חבית של יין ביד כותי, ושל ציר ושל מורייס ביד גוי, אם מכיר חותמו וסתמו ⁠— מותר, אם לאו ⁠— אסור!

from the following baraita: With regard to one who sends a jug of wine in the hands of a Samaritan, or a jug of fish brine or a jug of fish stew in the hands of a non-Jew, if he recognizes his seal and his manner of closing the jug, it is permitted; if he does not recognize them, it is prohibited. Apparently, a sealed jug is permitted only when it is recognizable.

אמר רבי זירא: לא קשיא ⁠— כאן בעיר, כאן בדרך.

R' Zeira said that this is not difficult. Here, the first baraita is referring to jugs located in a city; there, the second baraita is referring to jugs that the Samaritan carries on the road. Sealed jugs are permitted in a city because the Samaritan is careful to ensure that non-Jews do not touch them in front of anyone, so that he does not forfeit the business of Jews. While traveling he is not concerned, as he assumes that no one will discover that the non-Jew came into contact with the wine.

מתקיף לה רבי ירמיה: מידי הנך דעיר לא בדרך אתו? אלא אמר רבי ירמיה: בין הגיתות שנינו, כיון דכולי עלמא אפכי, מירתת, אמר: השתא אי חזו לי מפסדו לי.

R' Yirmeya objects to this: Didn’t these jugs located in the city come by the road as well? Rather, R' Yirmeya says: We learned the baraita that permits sealed jugs only in reference to those that are located between the winepresses. Since everyone is found there, the Samaritan is apprehensive, as he says to himself: Now, if someone sees me allowing a non-Jew to handle the wine they will cause me to lose my profit, as Jews will not purchase it.

אתמר: מפני מה אסרו שכר של גוים? רמי בר חמא אמר רבי יצחק: משום חתנות, רב נחמן אמר: משום גילוי.

It was stated: For what reason did the rabbis prohibit the beer of non-Jews? Rami bar Ḥama says that R' Yitzḥak says: It is due to the concern that Jews will befriend non-Jews while drinking with them, which might lead to marriage with non-Jews. Rav Naḥman said: It is due to the concern of exposure.