Negative Commandment #83
Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
Second Section – the Negative Commandments
83. It is a negative commandment "do not use improper weights and measures"
As it states in Vayikra (Leviticus) 19:35, "do not use improper mishpat, midah, mishkal, or mesura." Our Sages of blessed memory have stated 'mishpat' means the system of sizes. 'Midah and mishkal' means do not take away from the size or weight what was agreed upon by the people of the country. Also, do not mislead another person regarding the size of land. 'Mesura' means the Torah is strict even about a small amount like a mesura, which is 1/36 of a log.
A person who transgresses this has neglected a positive commandment ("a person should have proper scales" - Vayikra 19:36) and also disobeyed this negative commandment. Even if a person gives an improper measurement or weight to a non-Jew, he has transgressed this commandment, and he is required to return it. It is forbidden to mislead a non-Jew in accounting and this is included in the law stated in Devarim (Deuteronomy) 25:16, "for this is an abomination to G-d... all who do wrong."
A court is required to hire people to check the stores to make sure the scales and measurements are proper and to establish prices. If someone has improper scales, measurements, or weights, they should be removed from him and he should be fined. If someone sells items at a higher price, he should be forced to sell at the lower market price. The punishment for one who transgresses the laws of weights and measures is more strict than illicit relations, as the one who is guilty with weights and measures is like a person who denies the exodus from Egypt.
This applies in all places and at all times, for men and for women.