Mishnayos Bava Metzia Perek 4 Mishnah 11

One may not intermingle produce bought from one supplier with other produce, even if he intermingles new produce with other new produce and ostensibly the buyer suffers no loss from his doing so. And needless to say, one may not intermingle new produce with old produce, in the event that the old produce is superior, as with grains, since intermingling lowers its value. Actually, they said: With regard to wine, they permitted one to mix strong wine with weak wine, because one thereby enhances it. One may not intentionally mix wine sediment with the wine, but one may give the buyer wine with its sediment; the seller is not required to filter the wine. One who had water mix with his wine may not sell it in the store, unless he informs the buyer that it contains water. And he may not sell it to a merchant, even if he informs him of the mixture, as, although he is aware that there is water mixed with the wine, it will be used for nothing other than deceit because the merchant will likely not inform the buyer that it is diluted. In a place where they are accustomed to place water into the wine to dilute it and everyone is aware of that fact, one may place water in the wine.

אֵין מְעָרְבִין פֵּרוֹת בְּפֵרוֹת, אֲפִלּוּ חֲדָשִׁים בַּחֲדָשִׁים, וְאֵין צָרִיךְ לוֹמַר חֲדָשִׁים בִּישָׁנִים. בֶּאֱמֶת, בְּיַיִן הִתִּירוּ לְעָרֵב קָשֶׁה בְרַךְ, מִפְּנֵי שֶׁהוּא מַשְׁבִּיחוֹ. אֵין מְעָרְבִין שִׁמְרֵי יַיִן בְּיַיִן, אֲבָל נוֹתֵן לוֹ אֶת שְׁמָרָיו. מִי שֶׁנִּתְעָרֵב מַיִם בְּיֵינוֹ, לֹא יִמְכְּרֶנּוּ בַחֲנוּת אֶלָּא אִם כֵּן הוֹדִיעוֹ, וְלֹא לְתַגָּר אַף עַל פִּי שֶׁהוֹדִיעוֹ, שֶׁאֵינוֹ אֶלָּא לְרַמּוֹת בּוֹ. מְקוֹם שֶׁנָּהֲגוּ לְהַטִּיל מַיִם בַּיַּיִן, יַטִּילוּ: