1) ONE WHO AGREES TO BUY A FIELD AND THEN CHANGES HIS MIND
QUESTIONS: The Gemara discusses a case in which Shimon agrees to buy a field from Reuven, and then complaints of claimants ("Asikin") are heard about the field. Shimon may withdraw from purchasing the field as long as he has not yet taken ownership of it with a Chazakah. Once he has taken ownership, he cannot cancel the sale. RASHI explains that Shimon may withdraw only when he has not yet given any money to Reuven for the land. If Shimon has given money, he has performed an act of acquisition and he may not withdraw from the sale.
The Gemara asks what form of Chazakah constitutes the buyer's taking ownership of the field, and it answers that his Chazakah occurs from the time he treads upon the boundaries of the field ("Dayish a'Mitzri").
There are a number of unclear points in the Gemara.
If Shimon has not yet performed an act of acquisition (such as giving money to Reuven), it is obvious that he has not yet taken ownership and he may cancel the sale.
Moreover, why does the Gemara here ask what constitutes a Chazakah? The Mishnah in Bava Basra (42a) clearly lists the forms of actions necessary to make a Chazakah of ownership on a field: "Na'al" (locking), "Gadar" (fencing in), and "Paratz" (making a breach in a fence to create an entrance), or any act done to enhance the land such as digging. Also, why does the Gemara give a different form of Chazakah (treading on the boundaries, which is a lesser display of one's taking title to the field) from the ones listed in the Mishnah in Bava Basra? (TOSFOS DH u'Me'eimas)
ANSWERS:
(a) TOSFOS answers that in the case of the Gemara here, Shimon already gave money to Reuven for the field, but where they live it is the practice to transfer ownership of a field by writing a Shtar in addition to giving payment for the field. Although payment for the field does not transfer ownership of a field in such a place (Kidushin 26a), it does enable the buyer to take possession by using a weaker form of Chazakah. Accordingly, the Gemara here asks what forms of Chazakah are needed when a buyer has already given money for the field, while the Mishnah in Bava Basra discusses the forms of Chazakah needed when the buyer has not yet given money for the field.
(b) Tosfos cites the RIVAM who answers that the Gemara here is not asking what form of Chazakah is needed in order to transfer ownership of the field to the buyer. Rather, the acquisition of the land has already taken place, but the buyer still has the right to cancel the sale. The Gemara is asking what act demonstrates that the buyer forfeits his right to cancel the sale.
According to the Rivam, the acquisition of the field in this case is not performed with money and a Shtar, because if it is, the acquisition would be complete and final and the buyer would not be able to change his mind and cancel the Kinyan. Rather, the acquisition of the field is done through a Kinyan Sudar, or Chalifin (SHITAH MEKUBETZES). In such a case the Rabanan instituted that although the transfer of ownership occurred, the buyer may still withdraw from the sale if he hears complaints of claimants ("Asikin") about the field, until a certain point. (Rivam compares this to the enactment of the Rabanan that after a Kinyan Sudar, a buyer is allowed to withdraw from the deal "all the time that they are involved in the matter.") Kinyan Sudar is not a display of absolute intent to finalize the Kinyan under all circumstances until it is followed by an act that denotes some form of permanence.
(c) The RITVA explains in a manner similar but not identical to the Rivam's. He explains that regardless of what form of Kinyan is used to acquire the field, the buyer may revoke the sale upon hearing the complaints of claimants until a certain point. However, this is not because the buyer has not completely finalized the sale and may still withdraw. The reason why the sale may be cancelled is that if claims are made against the field before the purchaser even has a chance to tread the boundaries of the field, the purchase is like a "Mekach Ta'us." That is, the buyer may say that he certainly did not intend to buy the field under such circumstances and that the seller misled him about the details of the field.
TOSFOS in Bava Kama (9a, DH mi'she'Hichzik) answers similarly to the Ritva, but adds that if the buyer has not only made a Kinyan Shtar or Chazakah but has even given money to the seller, he certainly cannot change his mind even if he has not yet "tread upon the boundaries." The buyer retains the right to revoke the Kinyan only until the entire process is complete -- which happens when the buyer gives the money to the seller and the seller is no longer dealing with the buyer. At that point, even if the buyer has not yet "tread upon the boundaries," the sale is final and the buyer cannot revoke the Kinyan.
2) RELINQUISHING ONE'S SHARE AT THE EXPENSE OF ANOTHER PERSON
QUESTIONS: The Mishnah discusses the case of a man who was married to three wives and died without enough money to pay each one her full Kesuvah. The Kesuvah of the first wife was 100 Zuz, the Kesuvah of the second wife was 200 Zuz, and the Kesuvah of the third wife was 300 Zuz. If the man died leaving only 100 Zuz, all three women divide it equally, each taking 33 1/3 Zuz. RASHI explains that they divide it equally because they each have a claim to that 100 Zuz.
If, however, he left 200 Zuz, the Mishnah says that the first wife receives 50, and the second and third wives each receive 75. If he left 300 Zuz, then the first wife receives 50, the second wife receives 100, and the third wife receives 150.
The Gemara immediately asks that it does not make sense to give the first wife 50 Zuz when the husband left 200 Zuz. Since the Kesuvah of the first wife is only 100 Zuz, she has a claim to only the first 100 Zuz that her husband left (so that she receives 33 1/3 of that money). She has no claim to the second hundred Zuz that he left. Why does she receive 50 Zuz?
Shmuel answers that the Mishnah refers to a case in which the second wife relinquished her claim to the first 100 Zuz. Hence, only the first and third wives divide it, so that each gets 50 (see Chart). The Gemara then asks that if the second wife relinquished her claim to the first 100 Zuz, then why does the Mishnah say that when the husband left a total of 200 Zuz, both the second wife and the third wife receive 75 Zuz? The third wife should receive 100 (50 from the first 100 Zuz which she split with the first wife, and 50 from the second 100 Zuz which she split with the second wife), and the second wife should receive only 50! The Gemara answers that when the second wife relinquished her claim to the first 100 Zuz, she did so only with regard to the first wife; she did not want the first wife's portion to be decreased because of her, and therefore she relinquished her claim. However, she does not want to relinquish her claim to that money when it comes to dividing it with the third wife. Hence, of the remaining 50 Zuz (from the first hundred), she receives 25 and the third wife receives 25.
(a) The Gemara's answer does not seem to be mathematically correct. Since each woman is supposed to receive an equal share of the first 100 Zuz, or 33 1/3 each, when the second wife relinquishes her share with regard to the first wife, the third wife's portion should not be affected. She still should receive her 33 1/3 from the first 100 Zuz, leaving the second wife only 16 2/3 Zuz. Why do the second and third wives receive 25 Zuz out of the first 100?
(b) Why does the Mishnah give such unusual cases to demonstrate the distribution of limited assets? The Mishnah should teach a simple case in which no one relinquished anything to anyone.
ANSWERS:
(a) The RITVA explains that the Gemara gives only the gist of the answer, but it leaves out a detail. Not only did the second wife relinquish her share of the first 100 Zuz to the first wife, the third wife consented to the second wife's statement and agreed that the first wife should come away with an entire half of the first 100 Zuz. Because the third wife also agreed to this, part of the amount which the first wife receives beyond her due share comes from the third wife's share. (That is, instead of the second wife giving the full 16 2/3 from her own share to the first wife, half of that (8 1/3) comes from the third wife's share. Hence, out of the first 100 Zuz, the first wife receives 50 (33 1/3 + 8 1/3 + 8 1/3), the second wife 25 (33 1/3 - 8 1/3), and the third wife 25 (33 1/3 - 8 1/3).)
(b) The RITVA writes that the Mishnah prefers to list cases of distribution of limited assets where those assets are divided into whole numbers. The simple cases, where no wife relinquished her shares, involve divisions of the assets into non-integers (such as 33 1/3).

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