Halakhah zu Wajikra 19:35

To not cheat in measures, and all measures are included: To not cheat in liquid and dry measures, and not with scales; and included in measures is also the measuring of lands; and anything that is measured by people, such as clothes and that which is similar to them - as it is stated (Leviticus 19:35), "You shall not pervert justice with measures of length, weight, or capacity (mesurah)." And they, may their memory be blessed, explained (Bava Metzia 61b) that mesurah is a liquid and a dry measure; and it is the smallest measure, as it is one thirty-third of a log. And we learn from this that the Torah is concerned about the smallest amount with measures; meaning to say that even though the Torah was only concerned about [the value of] a small coin with other thefts, regarding measures, it was concerned about the smallest amount.

From the laws of the commandment is, for example, that which they, may their memory be blessed, said (Bava Batra 89a), that we do not make weights out of tin and lead and from any of the other types of metal, since they bring up rust and become lacking, but we [rather] make them out of stone and glass and what is similar to them; and the things that they said regarding the measurement of land; and that which they taught us about the shape of the leveler, that they call rasero in the vernacular. And they also said (Bava Batra 89b) that he should not cause foam in a liquid measure at the time that he measures, and even if it was the smallest measure. As behold, we have found that the Torah is concerned with measures about the smallest amount. As it is stated (Leviticus 19:35), "You shall not pervert justice with measures of length, weight, or capacity (mesurah)"; and mesurah is the smallest measure, as it is one thirty-third of a log. And the sizes that they, may their memory be blessed, gave to the length of the bar of the scales and the length of the strings; and the distinction that they said between scales that are made to weigh one type and the scales for another type; and that which they said that the court is obligated to set up supervisors in each and every place to make rounds to regulate the scales and weights, and they have the authority to fine the money, and [even] the body of anyone with whom lacking scales are found; and the rest of its details [are] in the fifth chapter of [Bava] Batra (see Tur, Choshen Mishpat 231).

He prohibited the doing of inequity in the measurement of land and of weights. And that is His saying, "You shall not commit injustice in judgement; in measure, etc." (Leviticus 19:35). And the explanation of the verse according to that which appears in the tradition about it is, "You shall not commit injustice in the judgement of the measure." And they said in explanation of the content of this negative commandment (Sifra, Kedoshim, Chapter 8:5), "'You shall not commit injustice in judgment' - if this is to a judge, it is already written, (viz. Leviticus 19:15). If so, why is it stated, 'in judgment?' It is to teach that a measurer is called a judge." And there (Sifra, Kedoshim, Chapter 8:6), they said, "'Of the measure' - that is the measure of the land" - meaning to say, the measuring out and its division that one does upon it should be according to that which is required by the rules of mathematics that are exacting in measure, and knowledge of the true geometry for [use upon] them; and that he should not use imagined reckonings for this - as is done by most of the people - for they lack truth. "In weight," includes weights and scales. (See Parashat Kedoshim; Mishneh Torah, Theft 6.)