Avodah Zarah 73a
עבודה זרה ע״ג א — ד"ה מַתְנִי׳ יֵין נֶסֶךְ אָסוּר וְאוֹסֵר בְּכׇל
Avodah Zarah 73a:2
The Talmud discusses the nullification of yayin nesech (wine poured as a libation) in a mixture, establishing that it can be batel only when its ratio falls below a certain threshold, and debating the rules of bitul for forbidden substances that give flavor.
מַתְנִי׳ יֵין נֶסֶךְ אָסוּר וְאוֹסֵר בְּכׇל שֶׁהוּא, יַיִן בְּיַיִן וּמַיִם בְּמַיִם בְּכׇל שֶׁהוּא, יַיִן בְּמַיִם וּמַיִם בְּיַיִן בְּנוֹתֵן טַעַם. זֶה הַכְּלָל: מִין בְּמִינוֹ — בְּמַשֶּׁהוּ, וְשֶׁלֹּא בְּמִינוֹ — בְּנוֹתֵן טַעַם.
MISHNA: Wine used for a libation is forbidden, and any amount of it renders other wine forbidden if they are mixed together. Wine used for a libation that became mixed with wine, or water that was used for an idolatrous libation that became mixed with ordinary water, renders the mixture forbidden with any amount of the forbidden wine or water; but wine used for a libation that became mixed with water, or water used for a libation that became mixed with wine renders the mixture forbidden only if the forbidden liquid is sufficient to impart flavor to the mixture, i.e., for the wine to flavor the water or for the water to dilute the wine to an extent that can be tasted. This is the principle: A substance in contact with the same type of substance renders the mixture forbidden with any amount of the forbidden substance, but a substance in contact with a different type of substance renders the mixture forbidden only in a case where it imparts flavor to it.

