1) "B'SIMANAV UV'METZARAV"
OPINIONS: The Mishnah teaches that when one sells land and says, "... with these landmarks and with these boundaries," he is allowed a margin of error of up to one sixth. The RASHBAM (DH b'Simanav) explains that the Mishnah refers to the same case which it has been discussing until now, a case in which one sells a Beis Kor of "Afar" (earth). The only difference is that in this case, the seller specifies the field's landmarks and boundaries.
What exactly is the novelty of this case in contrast to the other cases which the Mishnah has discussed, such as "Midah b'Chevel" ("by the measure of the rope") and "Hen Chaser Hen Yaser" ("whether less or whether more")?
(a) The RA'AVAD (cited by the Shitah Mekubetzes) understands that this case is unique. In all of the previous cases, the buyer purchases an specific amount of land sight unseen. Accordingly, the amount is more important in those cases, because the amount is the only information about the land the buyer has. Of course, if he accepts the terms of "Hen Chaser Hen Yaser," then he must allow for some inaccuracy in the measurements. In contrast, in the case of "b'Simanav uv'Metzarav," the buyer has seen the field and its boundaries, and he has accepted upon himself to buy that piece of land. Accordingly, he also accepts to buy the land at its present size, unless a large discrepancy (one sixth) between the stated size and the actual size is discovered. This is also the explanation of the TOSFOS YOM TOV.
(b) The RE'EM (cited by the Shitah Mekubetzes) disagrees with the Ra'avad. He explains that "Midah b'Chevel" is a case of a precise measurement, where the seller must account for the entire amount that he committed to sell. In the case of "Hen Chaser Hen Yaser," the seller explicitly gives an imprecise measure in order to allow for a discrepancy of up to one quarter Kav per Se'ah. The case of "b'Simanav uv'Metzarav" is in between the two previous cases. On one hand, the seller specifies boundaries. On the other hand, he does not mention a precise size, only the area that contains this amount (Beis Kor) of earth being sold. Therefore, the seller is allowed a margin of error of up to one sixth of the Beis Kor.
The Re'em's explanation seems difficult. The Ra'avad seems to give a simple difference based on the fact that a margin of error of one sixth is much greater than the margin of error allowed in the previous cases, even that of "Hen Chaser Hen Yaser" (one quarter Kav per Se'ah). It follows that the case of "b'Simanav uv'Metzarav" in not in between the cases of "Hen Chaser" and "Midah b'Chevel," but rather it is the most extreme amount of error allowed. How can the Re'em argue with these numbers? The Re'em's intent seems unclear, unless one suggests that he in fact does not disagree with the Ra'avad (in which case the Shitah Mekubetzes is difficult to understand, because he cites the Re'em as a second explanation). (Y. MONTROSE)
2) TWO BROTHERS DIVIDE AN ESTATE, AND A THIRD BROTHER THEN APPEARS
OPINIONS: The Gemara discusses a case in which two brothers divided their father's estate after his death, and then a third brother arrived from overseas. Rav rules that the division is invalid. Shmuel rules "Mekamtzin" -- "they must be frugal." What does Shmuel mean?
(a) The RASHBAM (DH Mekamtzin) explains that each of the first two brothers must give a third of his portion to the third brother. For example, if each brother originally received three fields, each he must choose one field and give it the third brother. In this way, every brother ends up with two fields.
(b) TOSFOS (DH u'Shmuel) disagrees with this explanation. Why should the first two brothers have the right to choose what property they receive, while the third brother must receive the less desirable portions? Tosfos explains instead that "Mekamtzin" means that new lots are drawn to divide the existing fields of the brothers. For example, if there were three fields to divide, and the first two brothers originally took one field each and split the third, lots are drawn when the third brother arrives to determine his portion. If he draws the lot of the third field, that field becomes his, and the other brothers retain possession of their respective fields. If the third brother draws the lot of one of the other brothers' fields, the brothers keep their halves of the third field and split the remaining field. This is in contrast to Rav's opinion that an entirely new lottery is performed, and none of the brothers have possession of any fields before the lottery.
(c) The RASHBA and others quote the RI MI'GASH who gives a different explanation. He explains that when Shmuel says "Mekamtzin," he means that if the third brother is satisfied with what the other two brothers have given to him, the division is considered valid. If, however, the third brother is not satisfied, Shmuel agrees that the entire lottery must be performed again. In what way does Rav disagree? Rav maintains that even one of the original two brothers may demand to have a new lottery instead of having to divide up his current portion, even against the will of the other two brothers. (Y. MONTROSE)