Bava Basra Chapter 7, Mishnah 3. We are nearing the end of the chapter and the conclusion of the discussion regarding how sales are conducted. This mishnah is broader than the previous ones: the question it comes to answer is what the halachah is regarding a person who said two things almost in the same breath, where the second statement contradicts the first. Such a sentence is incoherent, and the question is whether we interpret his intention based on the first expression, the second expression, or whether we are left in doubt.
The two types of sale that we learned:
"Middah bechevel ani mocher lach" - an exact sale, according to measurement with a rope.
"Hen chaser hen yeseir" - a sale of an estimated amount, an approximate beis kor.
Our mishnah asks: what is the halachah when a person uses both expressions together and says "Middah bechevel ani mocher lach, hen chaser hen yeseir" - meaning, I am selling you a kor of land exactly, approximately. Which expression prevails?
The opinion of Ben Nannas:
The mishnah brings only one opinion, the opinion of Ben Nannas: the second thing the person said comes to retract and correct his first statement, and therefore it nullifies the first statement, and we follow the second statement. This is the wording of the mishnah: "Biteil hen chaser hen yeseir middah bechevel" - a sentence that is difficult to parse, meaning that the second statement, "hen chaser hen yeseir", nullifies the first, "middah bechevel".
And the same is true in the reverse order, teaching us that the matter does not depend on whether the expression is exact or approximate, but simply on the fact that it is the second expression: if he first said "Hen chaser hen yeseir" and then "Middah bechevel" - "Biteil middah bechevel hen chaser hen yeseir", again the second thing stated prevails over the first, and the first is nullified. These are the words of Ben Nannas.
The opinion of the Sages:
Seemingly, the discussion ends here, as the mishnah moves on to a new topic. However, the Gemara teaches that the Sages argue with Ben Nannas and hold that we are in doubt: we do not know if the person intended to nullify the first expression with his second expression or not, and we are left in doubt.
In this case, since the speaker is the seller, he is the one who determines what he meant by his words, and we must believe him. The buyer, on the other hand, is seeking to extract additional value from the sale, and upon him falls the rule of "hamotzi meichaveiro alav hara'ayah". Since we do not know whom to believe, we believe the one who made the statements, who is also in possession of the land and the property - and therefore he has the upper hand.
According to the Sages, therefore, the seller may say what he intended, whether it was an exact measurement or an estimated measurement, and naturally he will choose the expression that is to his advantage:
If he sold a beis kor and it turned out that the field amounts to 1.01 beis kors, he will say: I intended an exact beis kor, and the remainder belongs to me.
And if it turned out that the field amounts to 0.99 of a beis kor, he will say: I intended an approximate beis kor, and the sale stands as it is, and the buyer receives 0.99 of a beis kor.
This is how the Sages rule, and this is the halachah - the halachah follows the Sages.
A sale by its marks and boundaries:
The second part of the Mishnah deals with a new case. Until now we learned two ways of selling a beis kor: an approximate sale of "whether less or more," where the permitted deviation is up to one twenty-fourth (a little over four percent), and an exact sale of "measured by a rope," where an exact measurement is required. Now the Mishnah teaches a third possibility: a seller tells the buyer that the field is specific and defined, and the buyer sees its boundaries with his own eyes - a field surrounded by a fence, or a field bounded by a river on the south, a fence on the north, a tree on the east and a rock on the west. The buyer sees exactly what he is getting.
In such a case, if the seller added and said "and it is a beis kor," we permit an even greater deviation than that of "whether less or more," since the buyer knows what he is getting. Here we return to the rules of onaah (price fraud) learned in Bava Metzia, which state that it is forbidden to defraud a seller or buyer by overcharging or underpaying, but a tolerance margin of a shtus (one sixth) is granted. Here too, when it is clear to the buyer's eyes what is being sold and an estimated size is given to the field, a deviation of up to a shtus is permitted - a little over sixteen percent - and not just one twenty-fourth.
This is what the Mishnah says: "Besimanav uv'meitzarav pachus mishtus higi'o, ad shtus yenakeh" - If it was sold by its marks and boundaries and the discrepancy was less than a sixth, the buyer receives it; if it reaches a sixth, they must deduct. "Besimanav" - when it is sold according to its marks, from the tree here to the rock here; "uv'meitzarav" - according to its boundaries, the street on this side and the river on this side. The meaning of this is: if the discrepancy is less than a sixth, the sale stands; but if it is greater than a sixth, the sale does not stand as is.
The practical calculation:
A beis kor is one hundred and eighty kav, since there are six kav in a se'ah and thirty se'ah in a kor. A shtus (one sixth) is thirty kav, and therefore as long as the field ranges between one hundred and fifty and two hundred and ten kav - the sale stands. But if the deviation is greater than this:
If it turns out that the field has only one hundred and forty-nine kav, the discrepancy exceeds a shtus. If the price of a kav is one thousand dollars, the buyer paid one hundred and eighty thousand dollars, and the seller must refund him thirty-one thousand dollars.
And if it turns out that the field has two hundred and eleven kav, we have again exceeded the measure, so the seller takes back thirty-one kav of land, and the buyer is left with exactly one hundred and eighty kav.
To explain the complex phrasing "ad shtus yenakeh" - up to a sixth, he must deduct: when the deviation is large - fifty percent, forty percent or thirty percent - the transaction must be corrected and set to the standard, all the way down to the shtus. Down to that point, and this is the meaning of "up to" when looking from this direction, "he must deduct" - we adjust things by deducting the cost, so that the transaction is fair.
In summary: In this Mishnah we learned two matters. First - when the seller uses two contradictory expressions, Ben Nannas holds that the second expression cancels the first, whereas the Sages hold that we are in doubt, and the seller has the upper hand as the one in possession of the property, and the halachah follows the Sages. Second - for a field sold by its marks and boundaries, where the buyer sees its borders with his own eyes, the permitted margin of deviation is wider: not one twenty-fourth but a shtus, and for anything deviating beyond that - we deduct and correct the transaction.