LEV807 It is a negative commandment to do no wrong with any measures or weights for Scripture says, You shall do no wrong in mishpat, in size, in weight, or in m'surah [this verse]; and the Sages of blessed memory interpreted (Sifra, ibid.: mishpat means the system of standards; "in size, in weight" -- that nothing should be lacking from the [standard] size or weight as the people of the country have agreed upon it; and so likewise not to mislead one's fellow-man in the measurement of land. "Or in m'surah" -- the Torah was particular even about a small quantity like a m'surah, which is a thirty-sixth part of a log. If someone transgresses this, he disobeys a positive commandment (Just balances… and a just hin shall you have-- Va-yikra 19:36), and he violates this prohibition. Even if he gives a heathen a short measure or weight, he violates this, and is duty-found to return [the amount lacking]. It is forbidden to mislead a heathen in an accounting; this is included in the scope of the verse, For all ... that do wrong are an abomination to Hashem your God (D'varim 25:16). The court has a duty to appoint officials to make the rounds among the stores and shops to correct the scales, weights and measures, and to establish market prices. If someone's measures, weights or scales are not accurate, they are to take them away from him and to penalize him with a fine. If someone charges above the going prices, they are to compel him to sell at the market prices. The punishment [by Heaven] over weights and measures is more severe than a punishment for immorality; he [the guilty person] is as one who denies the exodus from Egypt.