The article deals with the understanding of the historical and legal components of the law prohibiting fraud (honayah) as appears from the Bible to Rabbinic literature. The first section reviews this law and its understanding from Biblical times until the destruction of the Second Temple. Then follows a discussion of the changes that arose after this period, based on the information gleaned from the rabbinic literature, on fraud, its development, and its structure. The law declares that every deviation of one sixth of an accepted price is called fraud. The article analyzes the main issues of the law such as: is this sixth of the gross price or of the net price? How can one set the legal definitions of profit and fraud for an object that was resold several times. The authors analyze cases in which it is difficult to set a price due to various reasons, or items that both the buyer and seller cannot complain of fraud. The rabbinic law is compared and contrasted to the contemporary Roman law.