יורה דעה קכ״וYoreh De'ah 126

Se’if 1א׳

הַמְּעָרֶה יַיִן לְתוֹךְ כְּלִי שֶׁיֵּשׁ בּוֹ יֵין עוֹבֵד כּוֹכָבִים הָאָסוּר בַּהֲנָאָה, נֶאֱסָר כָּל הַיַּיִן שֶׁבַּכְּלִי הָעֶלְיוֹן, שֶׁהֲרֵי הָעַמּוּד הַנִּצּוֹק מְחַבֵּר בֵּין הַיַּיִן שֶׁבַּכְּלִי הָעֶלְיוֹן וּבֵין הַיַּיִן שֶׁבַּכְּלִי הַתַּחְתּוֹן, וְרוֹאִים כְּאִלּוּ יַיִן שֶׁל הָאִסוּר מְעֹרָב בְּשֶׁל הֶתֵּר. וְאִם עֵרָה וְקִטֵּף, שֶׁקֹּדֶם שֶׁנָּגַע בְּשֶׁל הָאִסוּר הִפְסִיק קִלּוּחַ הַיּוֹרֵד מֵהַיַּיִן שֶׁל הֶתֵּר, מֻתָּר.

One who pours wine into a vessel in which there is the wine of an idolater (oved kokhavim — the standing term for a gentile) that is forbidden in benefit: all the wine that is in the upper vessel has become forbidden, for the column of the nitzok (the unbroken stream of poured wine) joins between the wine that is in the upper vessel and the wine that is in the lower vessel, and we regard it as though the forbidden wine were mixed with the permitted. And if he poured and cut off — that is, before it touched the forbidden wine he broke off the stream that was running down from the permitted wine — it is permitted.

Se’if 2ב׳

הָא דְּנִצּוֹק חִבּוּר, הָנֵי מִלֵּי בְּהֶפְסֵד מֻעָט, אֲבָל בְּהֶפְסֵד מְרֻבֶּה כְּגוֹן שֶׁהוֹצִיא מֵהֶחָבִית לִכְלִי שֶׁיֵּשׁ בּוֹ יַיִן נֶסֶךְ, מֻתָּר הַגָּה: וְאֵין חִלּוּק בֵּין אִם הָיָה הַרְבֵּה יַיִן בֶּחָבִית אוֹ לֹא. וַאֲפִלּוּ יָכוֹל לְמָכְרוֹ לְעוֹבֵד כּוֹכָבִים. וְכָל מַה שֶּׁהוּא בַּקַּנְקַן אוֹ בַּכּוֹס, מִקְרֵי הֶפְסֵד מוּעָט. וְדַוְקָא בְּיַיִן נֶסֶךְ, אֲבָל בִּשְׁאָר אִסּוּרִים אִם יָכוֹל לְמָכְרוֹ לְעוֹבֵד כּוֹכָבִים וְאֵין בּוֹ הֶפְסֵד מְרֻבֶּה, לֹא מִקְרֵי הֶפְסֵד מְרֻבֶּה (מַסְקָנַת ת"ה סִימָן ר"ד).

This, that a nitzok is a connection — these words are said in the case of a small loss; but in a case of great loss, such as where he drew out from the barrel into a vessel in which there is yayin nesach (wine poured out as an idolatrous libation), it is permitted. Hagah [Rema]: And there is no difference whether there was much wine in the barrel or not. And even if he is able to sell it to an idolater. And whatever is in the jar or in the cup is called a small loss. And that is specifically with yayin nesach; but with the other prohibitions, if he is able to sell it to an idolater and there is no great loss in it, it is not called a great loss (the conclusion of Terumat haDeshen, siman 204).

Se’if 3ג׳

נִצּוֹק בַּר נִצּוֹק אֵינוֹ חִבּוּר.

A nitzok from a nitzok is not a connection.