Shabbat 77A

תנינא: המוציא יין ⁠— כדי מזיגת כוס, ותני עלה: כדי מזיגת כוס יפה. וקתני סיפא: ״ושאר כל המשקין ברביעית״. ורבא לטעמיה, דאמר רבא: כל חמרא דלא דרי על חד תלת מיא לאו חמרא הוא.

learned that in the Mishnah: One who carries out undiluted wine is only liable if he carries out a measure equivalent to the wine typically diluted for a cup. And it was taught with regard to the Mishnah: A measure equivalent to the wine diluted for a significant cup of wine. And it was taught in the latter clause of the Mishnah: And the measure that determines liability for carrying out all other liquids is 1/4th of a log. Since 1/4th of a log is the significant measure for liquids, that is also the significant measure for diluted wine. And Rava is consistent with his line of reasoning, as Rava said: Any wine that does not hold one part wine diluted by 3 parts water is not wine. Wine must be sufficiently potent to be capable of being diluted with water 3 times its measure.

אמר אביי: שתי תשובות בדבר ⁠— חדא, דתנן: והמזוג שני חלקי מים ואחד יין, מן היין השירוני. ועוד: מים בכד ומצטרפין?!

Abaye said: There are two possible responses with regard to this matter. One, as we learned in a Mishnah: Diluted wine, which is used to determine the exact color of red, is two parts water and one part wine from the wine of the Sharon. Apparently, wine constitutes 1/3rd and not 1/4th of the diluted cup. And furthermore: Rava’s opinion is that the measure that determines liability for carrying out wine is a measure that, when diluted, would equal 1/4th of a log, i.e., 1/4th of 1/4th of a log of undiluted wine. Is it possible that the water is in the jug and yet joins together with the wine? The wine that he is carrying out is less than the required measure and is not fit for drinking.