“And when you sell an item to your friend or you buy from your friend…” (Vayikra 25:14)
It is a positive commandment that one should deal with the judgments of business dealings in the way that the Torah commanded. This means that there are situations when the sale is valid and other situations where the sale is not valid, and when weighing this up we are obligated to use the laws of the Torah. Although there are already other similar commandments as we have already seen in Parshas Mishpatim where we are commanded to judge between claimer and defendant or between damager and victim etc., we have nevertheless been given a special commandment here to give attention to the judgments of business, as it is a constant fact of life without which it would be impossible to live even for one day. This is the way of the Torah in many places that it specifies commandments and sometimes even repeats a commandment many times to stress its necessity or stringency. We see this especially with all of the many prohibitions about idol-worship, and Shabbos.
The root of these laws is well-known, as it is something which common-sense necessitates, for only with justice can civilization prosper.
This commandment applies in all places and at all times, both to men and to women.