How much of a deviation is permitted? TB Ketubot 98-99

Dappim TB Ketubot 98 and 99 litigate how much of a deviation of an agent (שליח) is considered a dereliction of duty and invalids the sale. The Gemara discusses the cases when the owner of a piece of land tells his agent to sell an acre and the agent only sells half an acre or the opposite when the owner of a piece of land tells his agent to sell ½ acre and the agent sells an acre. Is this deviation large enough to annul the agency and invalidate the sale?

The Gemara reframes the question and in my opinion answers it. A small deviation is permitted, but a large deviation is considered a dereliction of duty and the sale is an annulled.

“In continuation of the previous discussion, the Gemara raises another problem: It is obvious that if the employer said to his agent: Sell my property to one person, but not to two, and the agent sold the property to two people, since he said to him: To one, but not to two, it is certain that the agent has disregarded his instructions and is no longer considered an agent. However, if the employer said to the agent: Sell to one person, without specifying that he should not sell to two people, what is the halakha if the agent did sell the property to two people?

“Rav Huna said: The employer meant to sell to one person and not to two people. It is Rav Ḥisda and Rabba, son of Rav Huna, who both say: He meant to one person and even to two people. When he said to one person, he meant and even to one hundred people, as he did not mean one person specifically.

“Rav Naḥman happened to come to Sura. Rav Ḥisda and Rabba bar Rav Huna entered before him. They said to him: In a case like this one, which was discussed above in the Gemara, what is the halakha? He said to them: When he said to one person, he meant and even to two people. When he said to one person, he meant and even to one hundred people.

“Rav Ḥisda and Rav Huna said to him: Is the agent considered to be performing his assigned agency even though he erred, e.g., by selling property for less than its value? Rav Naḥman said to them: I do not say so in a case where the agent erred. They said to him: But didn’t the Master say that there is no prohibition against fraud in the sale of land, and land does not have a set value?

“He replied to them: This applies only where the homeowner erred, e.g., where he sold land for less than its market value. In that case, he cannot claim that the sale is invalid because of fraud. However, in a case where the agent erred, the homeowner can say to the agent: I sent you to act for my benefit and not to my detriment, and his appointment as an agent is nullified.

“The Gemara explains: And from where do you say that there is a legal difference between an error made by an agent and an error made by a homeowner?

“As we learned in a mishna (Terumot 4:4): In the case of one who says to his agent: Go out and separate the portion of the produce designated for the priest [teruma], the agent separates teruma in accordance with the mind-set of the homeowner. He must separate the amount that he assumes the owner would want to give, as there is no fixed fraction for the amount that one must set aside as teruma. A generous person would give as much as a fortieth of the produce as teruma, while a stingy person would give a sixtieth. And if he does not know the mind-set of the homeowner, he separates an intermediate measure, i.e., one-fiftieth of the produce. If he subtracted ten from the denominator and separated one-fortieth, or added ten to the denominator and separated one-sixtieth of the produce, his teruma is considered teruma.

“Whereas with regard to the homeowner himself it is taught in a baraita: If he separated teruma and even one-twentieth of the produce came up in his hand, his donation is effective and is considered teruma. The agent may deviate from the intention of the homeowner only within certain parameters. If he misunderstood the homeowner’s wishes and separated an unusually large percentage of the produce, his action accomplished nothing. The same action, however, when performed by the homeowner, is effective; if the homeowner himself mistakenly separated an unusually large percentage of his produce, it becomes teruma.” (Sefaria.org translation)  

According to Jewish law, a seller is not allowed to price gouge. The maximum profit halakha permits is 1/6. This is the first time that the Gemara explicitly says this rule is not applicable to the sale of land, that there is no prohibition against fraud in the sale of land-אֵין אוֹנָאָה לְקַרְקָעוֹת.” If the land is appraised at $100 and the buyer is willing to spend $1000 for their parcel of property, the owner may sell it to him at that price. However as in most cases, there are poskim who hold that the seller may not inflate the price of the land more than 50% of its appraised value.