Rambam - 1 Chapter a Day

The commentaries note that with regard to the prohibition against ona’ah (Chapter 12, Halachah 1), the Rambam uses the term chavero (one’s colleague), implying a fellow Jew. In Chapter 13, Halachah 7, he explicitly states that the prohibition does not involve gentiles. With regard to deception, by contrast, the prohibition extends also to gentiles.
With regard to the prohibition against deceiving gentiles, see the Rambam’s Commentary on the Mishnah (Keilim 12:7), which castigates people from deceiving gentiles, explaining that violation of this prohibition also leads to the desecration of God’s name and the acquisition of undesirable character traits.

See Hilchot De’ot 2:6.

Sefer Me’irat Einayim 228:7 explains that this law applies even if there is no substantial difference in the price of the article.

Our translation is not literal and refers to activities that a person performs that appear to honor a colleague, but actually do not. For example, one should not beg a person to eat at one’s home when one knows he will not accept the invitation. One should not offer him gifts that one knows he will not accept. These examples are mentioned in Hilchot De’ot, loc. cit.

Bava Metzia 60b gives as an example: dyeing the hair of a servant so that an older man appears younger.

The exact term used by Bava Metzia, ibid., means “make his hair stand on end.”

To give a healthier and more comely expression.

I.e., which make meat look more attractive than it actually is.

Even if there is no difference in the quality of the meat, if the gentile desires to purchase kosher meat, that is what he must be given.

Although this improves the appearance of the grain, it also provides the purchaser with a quantifiable monetary benefit. One can see the difference in price between husked grain (beans) and ordinary grain.
In his Commentary on the Mishnah (Bava Metzia 4:12), the Rambam explains that a customer could tell by the husks of the grain whether the grain would cook easily or not. Nevertheless - although husking the grain prevents a customer from gaining this information - since no deception is involved, it is not forbidden.

This advertising technique is still followed today. Giveaways are used to lure customers to a store in the hope that they will purchase other items.

Even though this and the practice mentioned directly beforehand are techniques intended to generate customer volume and are often compensated for by higher prices on other items, this is not considered deception, for the customer is not compelled to buy any particular article.

I.e., two batches from different fields (Kessef Mishneh).

And the entire amount is sold as if it were freshly harvested.

And the produce that was harvested previously will not be able to be stored for the same amount of time (Maggid Mishneh).

Sefer Me’irat Einayim 228:19 explains that this follows Rashi’s interpretation of Bava Metzia 60a. The Tur and the Ramah (Choshen Mishpat 228:11) offer a different conception of that passage.

Literally, the Rambam’s words mean “between the wine vats.” At the time the wine is fermenting, the flavors of the two wines will mix naturally, without one’s impairing the flavor of the other.

I.e., the previous clause was speaking about an instance in which one mixed only a small quantity of the other wine. As such, its presence would not be detected and one would be deceiving the purchaser into thinking that the entire quantity of wine he was purchasing was of the same type. When a large amount of the other wine is used, the purchaser will be able to sense the addition. Hence, this is not considered to be deception.

The Shulchan Aruch (Choshen Mishpat 228:14) states that in a place where it is customary for the purchaser to taste the product he acquires, it is permitted to mix wine. If it is not customary for the purchaser to taste, this is forbidden.

I.e., if water became mixed with wine, after the fact the wine may be sold; it need not be destroyed.

And sell it to them without informing them that the wine has been watered down already. (In that era, the wines were far stronger and were always mixed with water before being drunk.)

For if the water is mixed with the wine while it is fermenting, it will acquire the flavor of the wine. The mixture will not taste like diluted wine (Maggid Mishneh).

The Shulchan Aruch (Choshen Mishpat 228:16) explains the rationale for this ruling. Anyone buying from a wine or grain merchant knows that the merchant does not produce all the wine or grain himself, but rather purchases from others. Thus, he is not purchasing from him under the perception that the entire quantity of produce will be the same.

The Shulchan Aruch [(ibid.), based on Rashi, Bava Metzia 60a] is more specific, explaining that the merchant should not purchase the majority of his produce from a source that has an excellent reputation and the rest from sources where the quality is not so high. For then he will gain an unjustified reputation for selling quality produce.

Since wine and oil are both natural products, over time the portions of the fruit suspended in the liquid settle, producing a certain degree of sediment. If separated from the liquid, this sediment may not be mixed with liquid again. For the purchaser desires that the wine or oil he purchases be as pure as the sample he was shown (Sejer Me’irat Einayim 228:25).

I.e., one need not leave the dregs at the bottom of the first container and suffer the loss.

Instead, the oil must be entirely pure. If the oil contains any dregs, the sale may be nullified.

And if the seller has only pure oil, he may give the purchaser only 98 1/2 measures of oil. The Rambam’s ruling is cited by the Shulchan Aruch (Choshen Mishpat 228:20). The Tur and the Ramah maintain that the seller may not give a lesser measure, but he may add 1 1/2 measures of dregs. The Lechem Mishneh indeed interprets the Rambam’s ruling in accordance with this interpretation.

A larger measure is given to compensate for the residue suspended in the oil.

I.e., since in Nisan the oil will generally not be cloudy, the quantity the purchaser receives is less, because the residue will not take up space. Rashi (Bava Metzia 40b) gives a different interpretation.

A kav is one sixth of a se’ah.

For legumes frequently grow among wheat.

The Hebrew term implies dried out by the wind.

This is the average amount of grain that will be spoiled.

For lentils are picked by hand and therefore usually become mixed with sand and pebbles (Bava Batra 94a). Because grains are reaped in a different manner, this measure does not apply with regard to them (Maggid Mishneh; Sefer Me’irat Einayim 229:1). The Siftei Cohen 229:1 differs with this view and maintains that as the Ram bam states in the final clause, a purchaser must accept one fourth of a kav of dirt when purchasing any form of produce, and this applies with regard to grain as well.

I.e., it is likely that ten percent of the figs will be inedible [Tur, Ramah (Choshen Mishpat 229:1)].

The bracketed addition was made on the basis of the Shulchan Aruch (Choshen Mishpat 229:1). It appears that there is a printing error in the Mishneh Torah. This is also indicated by certain authoritative manuscripts and early printings of the Mishneh Torah.

From the Rambam’s words, it appears that this applies even when we know that the seller did not purposefully mix sand into the produce. The Ramah mentions a difference of opinion on this matter, quoting views that state that if we certainly know that the seller did not mix any sand or pebbles into the produce he is selling, the purchaser must accept the produce from him even though the ratio of dirt exceeds the above measures.

The rationale is that any stipulation made by the participants in a business transaction is binding. Since the custom is well-known, it is assumed that both parties agreed to it and considered it to be part of their business transaction. This principle applies not only in this context, but with regard to all aspects of Jewish business law.

I.e., because it is permitted to sell produce while mixed with other substances if this is the local custom, the following law applies.

And thus by removing it, he causes his colleague a loss. See Sefer Me’irat Einayim 329:9, which explains that this is considered to be dina d’garmi and not grama dinezikin. See the notes on Hilchot Chovel UMazik 7:7 for an explanation of the distinction between these two terms.

The name of a portion of the coastal plain in Eretz Yisrael. Although the Rambam is quoting the Mishnah (Bava Batra 6:2), one wonders why this geographic fact is relevant if this law is universally applicable.

To prevent them from leaking. If they leak, or they are unattractive, the purchaser is not required to accept them (Rashbam, Bava Batra 97b).