Not only are we not permitted to use inaccurate scales, we are not even allowed to own one. When it comes to stealing, it’s very clear that the person desires to steal from another and is not concealing that intent. However, when it comes to using an inaccurate scale, the person is attempting to show that he is trying to be honest on the outside, but on the inside, he is being deceptive. Therefore, the Torah tells us to eradicate this behavior and not even to own such a scale. The lesson we learn questions the possibility that Jews - sons of Hashem and an actual part of Him- can be convinced by the Yetzer Horah to sin. The answer is offered with the mitzvah of not owning inaccurate scales. The Yetzer Horah tells you have scales; have measures. Follow all the laws of Torah perfectly, but in one little area, it’s not so important. He tries to give you a little bit of doubt here and there and that’s how he gets into our heads. Therefore, it’s vital that we have accurate scales so that everything is measured, perfect and strong in all the areas of our life.

לקו״ש כז-ב