"Honest balance, honest weights, an honest dry measure and an honest liquid measure, you shall have"—Leviticus 19:36.
We are commanded to have precise and "righteous" measuring implements—scales, weights, and measures.
The Midrash says: "Conditional on this I took you out of Egypt—on condition that you accept the mitzvah of [honest] measures. For one who acknowledges the mitzvah of measures, also acknowledges the Exodus from Egypt; and one who rejects the mitzah of measures, also denies the Exodus from Egypt."
"You shall do no unrighteousness in judgment; in measure, in weight or in land measure"—Leviticus 19:35.
It is forbidden to be dishonest in the course of surveying land, or measuring or weighing substances. When surveying land, it must be done according to the principles of engineering—not randomly, by "guess-timate," as is so often done.
"You shall not have in your bag diverse weights, large and small"—Deuteronomy 25:13.
It is forbidden to even harbor in one's possession an unbalanced weight or measuring implement—even if there's no intention to use them. As the Talmud says, "even if it is being used as a commode!"
