For the source text click/tap here: Ketubot 84
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Steinsaltz tells us:
An example that is brought by our is the case of ona’ah – unfair business practices. According to the Torah (See Vayikra 25:14, 17) business transactions must be fair and one side cannot take advantage of another. Thus, overcharging or underpaying is forbidden by the Torah, and the forbidden profits will need to be returned or the transaction voided. What would be the halakha if someone said to his friend “I am selling this to you on the condition that the rule forbidding ona’ah does not apply”? Here we find a disagreement between Shmuel who permits such a condition, permitting the sale and Rav who insists that ona’ah still applies.
The source for this discussion of ona’ah appears in Massekhet Bava Metzia (51a). In truth, it is not only a question of whether a person can make an agreement to dispense with the rules of the Torah about money matters, but also a more basic question of how to define the law of ona’ah. Some argue that ona’ah has two sides to it. On the one hand there is a question of money, on the other hand there are elements of issur – of forbidden practices – involved, as well. It is therefore possible that even if a person can choose to forgo the Torah rules about money, his agreement to forgo the rule of ona’ah will have no legitimacy because of the issur involved.
We review the Halacha of overreaching and the science behind deception .