Reference for Bava Batra 5:8
הַמּוֹכֵר יַיִן וָשֶׁמֶן לַחֲבֵרוֹ וְהוּקְרוּ אוֹ שֶׁהוּזְלוּ, אִם עַד שֶׁלֹּא נִתְמַלְּאָה הַמִּדָּה, לַמּוֹכֵר. מִשֶּׁנִּתְמַלְּאָה הַמִּדָּה, לַלּוֹקֵחַ. וְאִם הָיָה סַרְסוּר בֵּינֵיהֶן, נִשְׁבְּרָה הֶחָבִית, נִשְׁבְּרָה לַסַּרְסוּר. וְחַיָּב לְהַטִּיף לוֹ שָׁלֹשׁ טִפִּין. הִרְכִּינָהּ וּמִצָּה, הֲרֵי הוּא שֶׁל מוֹכֵר. וְהַחֶנְוָנִי אֵינוֹ חַיָּב לְהַטִּיף שָׁלֹשׁ טִפִּין. רַבִּי יְהוּדָה אוֹמֵר, עֶרֶב שַׁבָּת עִם חֲשֵׁכָה, פָּטוּר:
If one sells wine or oil to his neighbor, and they became dearer or cheaper — If (they became dearer or cheaper) before the measure were full, it is the seller's; if after, the buyer's. [We are speaking of a measuring vessel which belongs to neither and which was lent to both. It is lent to the seller until it is filled, and, thereafter, to the buyer. Therefore, before the measure has been filled, at which stage the vessel is lent to the seller, the buyer does not acquire. And after the measure has been filled, at which point the vessel is lent to the buyer, the buyer acquires.] And if there were a middleman between them and the jug [(which was his)] broke, it broke for the middleman (i.e., he is liable) [and we do not say that he is the messenger of the buyer and that it broke for the buyer.] And he [the seller] must "drip" for him [the buyer] three drops [of what adhered to the sides of the measuring vessel after the wine or oil were poured.] If he turned over and collected, it belongs to the seller [i.e., If he turned the measuring vessel over on its side after having poured the oil or the wine and "dripped" three drops, and the exudate of the measuring vessel collected in one spot at the bottom, it belongs to the seller, the buyer having "despaired" of it.] A shopkeeper need not "drip" three drops, [being preoccupied with selling.] R. Yehudah says: He is exempt [from doing so only] near nightfall on Sabbath eve. [The halachah is not in accordance with R. Yehudah.]