Negative Commandment #47
Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
Second Section – the Negative Commandments
47. It is a negative commandment "do not cheat another in buying and selling"
As it states in Vayikra (Leviticus) 25:14 , "When you sell... or buy from your friend, do not take advantage of your brother." If either a person cheats another knowingly or did not know he was overcharging, he is required to pay back the charges.
This applies in all places and at all times, for men and for women.