Negative commandment · Lo Ta’aseh #272 of 613
Not to possess two sets of weights and measures
שלא להיות אצלנו איפה ואיפה אבן ואבן
The verse · Devarim 25:14
לֹא־יִהְיֶה לְךָ בְּבֵיתְךָ אֵיפָה וְאֵיפָה גְּדוֹלָה וּקְטַנָּה
“Thou shalt not have in thy house divers measures, a great and a small.”
The Rambam’s words
Not to possess two sets of weights and measures, as [Deuteronomy 25:13] states: "You may not have in your home...."
שלא להיות אצלנו איפה ואיפה אבן ואבן, שנאמר "לֹא יִהְיֶה לְךָ בְּבֵיתְךָ אֵיפָה וְאֵיפָה" (דברים כה, יד).
Why · Sefer HaChinuch #602
To not hold over deficient weights and measures
“The root of the commandment of righteousness and the distancing from robbery and deceit among people is well-known to all intelligent people.”
Who & when
“And it is practiced in every place and at all times by males and females.”
Where in the Mishneh Torah
Hilchot Theft הלכות גניבה