Positive Mitzvah 208
Having Honest Measurements
Leviticus 19:36 "Honest balance, honest weights, an honest dry measure and an honest liquid measure, you shall have"
The next time you go to the fruit and vegetable store, take a look at how the owner weighs your bags at the counter. You'll notice that his cash register figures out your bill by multiplying the weight of your bag by the price per pound.
Did you know that the register must be periodically checked for malfunction? After all, its only a machine!
Imagine it's scale becoming unbalanced. You might end up paying more for your bag of fruit than it is worth because the scale is not weighing the fruit properly.
The Torah commands us to ensure the use of exact measuring units, to make sure we deal honestly with each other.
Negative Mitzvah 271
It is forbidden to falsify measurements
Leviticus 19:35 "You shall do no unrighteousness in judgment; in length, in weight or in measure"
Your mother likes to be sure she is getting her money's worth when she shops in a fruit and vegetable store.
When she pays for a five pound bag of potatoes, she trusts that she is getting five pounds and that the bag does not weigh any less.
The Torah commands us to make sure that we measure honestly when selling something by the pound, yard or any other measurement.
We may not use an approximate measure.
It is forbidden to cheat a customer and measure his purchase incorrectly.
Negative Mitzvah 272
It is forbidden to keep an unbalanced measure
Deuteronomy 25:13 "You shall not have in your bag diverse weights, one large and one small"
A person should not own, or even keep in his house, a scale or measuring tool that is not set or balanced to measure exactly.
If he does own such a measuring tool, he must throw it out, even if he wanted to keep it for other reasons besides business.