Baba Metzia 4:11-12

Baba Metzia 4:11

A seller is not permitted to mix produce from different sources together, not even if they are both new. It goes without saying that one may not mix new and old produce together. When it comes to wine, it is permitted to mix stronger and weaker wines because doing so improves it. Sediment from one wine may not be mixed with other wine (since this is not an improvement) but the seller may give the buyer the sediment of the same wine. If wine was mixed with water, he may not sell it in his shop unless he informs the customer. He may not sell it to a merchant even if he informs him because the merchant would likely use this diluted wine to cheat people (by selling it as if it were pure wine). In a place where the practice is to mix water into wine, they may do so.

Baba Metzia 4:12

A merchant may take grain from five granaries and put it into a single silo. He may take wine from five winepresses and put it into one large barrel so long as his intention is not to mix them (i.e., to mix poor wine with good wine and then to sell it as pure good wine). Rabbi Yehuda says that a shopkeeper may not give roasted grain or nuts to children because this trains them to come to him (and is therefore a form of unfair competition) but the Sages permit it. A shopkeeper may likewise not lower his prices (again, because of unfair competition) but the Sages say that one who does so will be remembered favorably. Abba Shaul says that a shopkeeper may not sift ground beans (in order to remove the waste and raise the price). The Sages permit this but they agree that he may not sift at the top of the bin because this makes the merchandise appear better than it is. When selling servants, animals or utensils, one may not beautify them to make them appear more valuable than they are.