The 271st prohibition is that we are forbidden to be dishonest in measurement of land, [liquid and dry] measures, or weights.

The source of this prohibition is G‑d's statement,1 "Do not be dishonest in law, measure, weight or volume."

The Oral Tradition explains that the verse means "Do not be dishonest in the law of measures." Our Sages2 said regarding the phrase "Do not be dishonest in law," "It cannot refer to passing judgment, because that was already stated.3 What, then, is the meaning of the word 'law'? To teach that one who measures is called a judge."

There our Sages also explained that the word "measure" refers to the measurement of land — that the measurement and calculation should be done according to the principles of engineering and methods of exact measurement, and not through inaccurate estimates, as is done by most officials.

The word "weight" includes both the weights and the balances.