OPINIONS: The Gemara (end of 51b) says in the name of Rebbi Yehoshua ben Levi that when one sells a house to his friend, the act of handing over the keys consummates the sale. The Gemara explains that the house is acquired through a separate Kinyan called "Chazakah," usage of the house.

However, when one sells a house he must first tell the buyer, "Go, perform an act of Chazakah, and acquire." Accordingly, Rebbi Yehoshua ben Levi must mean that when the seller hands over the keys to the buyer, it is equivalent to telling him, "Go, perform an act of Chazakah, and acquire." This is why the subsequent Chazakah is effective.

What exactly does this Kinyan Chazakah entail?

(a) TOSFOS (52a, DH Keivan) cites the RASHBAM in Bava Basra (53a, DH v'Hashta Ka'aili) who comments on the Gemara's statement there (52b) that when one locks the property of a convert who died with no heirs, he thereby acquires the convert's estate. The Rashbam explains that the Gemara does not mean that it suffices merely to lock the door with a key to acquire it through Chazakah. One must actually install a new lock on the door. According to the Rashbam, this seems to be the act of Kinyan discussed by the Gemara here.

Tosfos questions the Rashbam's explanation. The Gemara in Gitin (77b) relates an incident in which a Shechiv Mera (a dying man) wrote a Get for his wife before Shabbos but did not have time to give it to her before Shabbos arrived. On Shabbos, his condition deteriorated and he feared that he would die on Shabbos and that his wife would be forced to do Yibum with his brother (see Rashi there).

When Rava was asked what should be done, he replied that the dying man should give the part of his house where the Get was situated to his wife. She should proceed to lock the door and thereby acquire the place of the Get through the act of Chazakah of locking the door. The Gemara there clearly says that the act of Chazakah was the mere act of locking the door (and not the installation of a new lock, which is forbidden on Shabbos).

(b) Tosfos asserts that the act of locking the door alone suffices to effect a Chazakah. Tosfos adds that although the Rabanan prohibited acts of Kinyan on Shabbos, the Gemara in Bava Basra (156b) states that acquiring something from a Shechiv Mera on Shabbos is permitted. Since there is a concern that his condition will deteriorate if he knows that he cannot make a Kinyan, the Rabanan did not apply the prohibition in such a situation.

The SHITAH MEKUBETZES asks that although the prohibition against making a Kinyan on Shabbos is only mid'Rabanan while the prohibition against making a lock is mid'Oraisa, there appears to be a way in which making a lock may also be prohibited only mid'Rabanan, in which case Rava's ruling meant that the woman should make a lock for the door: telling a Nochri to perform a Melachah is prohibited only mid'Rabanan, and thus the woman could ask a Nochri to make a lock for the door for her.

The Shitah Mekubetzes answers that in this case, Rava would not have permitted the woman to ask a Nochri to do a Melachah (d'Oraisa) so that the Shechiv Mera could give a Get to his wife. (See also ROSH to Bava Basra 3:59.)

This answer is difficult to understand. The Gemara in Shabbos (129a) states that one may ask a Nochri to perform any Melachah (even a Melachah d'Oraisa; see MISHNAH BERURAH OC 328:47) on Shabbos for a sick person whose life is not in danger (provided that the sick person needs this Melachah; see Rashi there, DH Davar). Why, then, does the Shitah Mekubetzes assert that one may not ask a Nochri to do a Melachah d'Oraisa for a Shechiv Mera?

Perhaps when the Gemara in Shabbos states that one may ask a Nochri to perform a Melachah d'Oraisa for a sick person who is not in danger, it refers only to a situation in which one has no alternative way (that involves a lighter prohibition) to provide the patient with his needs. In the case of the Shechiv Mera, there was a preferable way to transfer the Get to the woman; the woman could do a transaction which is prohibited only mid'Rabanan. Although asking a Nochri to do a Melachah is prohibited only mid'Rabanan, since it involves a Torah prohibition (the Melachah which the Nochri performs) it is considered more severe than the Isur d'Rabanan against making a transaction on Shabbos. (D. Bloom, Y. Montrose)

QUESTION: The Mishnah (52a) teaches that when a person covers his Bor properly and nevertheless someone's ox or donkey falls in, the owner of the Bor is exempt from payment. How did an animal fall into the Bor if the owner covered it property? Rebbi Yitzchak bar bar Chanah explains that worms inside the cover caused it to decay.

The Gemara (52b) asks what the law is in the following case. A person covered his Bor with a cover which can bear only the weight of the oxen, but not the weight of camels. The cover eventually collapsed under the weight of oxen due to internal decay. Is the owner liable or not?

Perhaps, since the owner was negligent with regard to camels (he did not cover the Bor with a cover which could bear the weight of camels), the eventual collapse of the cover (due to worms) is also attributed to his negligence, and he is liable for the damage done to the oxen which fell into the Bor. On the other hand, since the damage that occurred was unrelated to his initial negligence with regard to camels, he is not liable.

The Gemara concludes that if the damage occurred only because of worms, the owner of the Bor is exempt even though he was negligent in preventing camels from falling into the Bor.

However, there seems to be another reason for why the owner of the Bor should be liable. This case seems to be a case of "Techilaso b'Peshi'ah v'Sofo b'Ones" - "starting off with negligence and ending up with forced circumstance." The Gemara (21b and elsewhere) discusses this concept at length (see Insights to Bava Metzia 93:3). The Amora'im disagree about whether a person is liable for damage which occurs due to circumstances beyond his control ("Ones") when he was initially negligent in preventing his property from doing damage. The Halachah is that one is liable in a case of "Techilaso b'Peshi'ah v'Sofo b'Ones." (See RAMBAM, Hilchos Nizkei Mamon 2:15). Why, then, does the Gemara here conclude that the owner of the Bor is exempt?

(a) TOSFOS (DH u'Shechichi) answers in the name of the RIVA that this Halachah applies only when the Ones occurred as a result of the Peshi'ah; that is, the damage which was beyond his control occurred only as a result of his original negligence. Accordingly, in the case of the Gemara here the owner cannot be liable because of "Techilaso b'Peshi'ah v'Sofo b'Ones," since the worms would have caused the cover to collapse regardless of whether the owner was negligent in the beginning or not. Even had the owner covered the Bor with a cover that could bear the weight of all types of animals, the collapse of the cover would have been beyond his control.

Tosfos cites support for this answer from the Gemara in Bava Metzia (36b). The Gemara there discusses the case of a guardian of a cow who was negligent and allowed a cow to escape. It wandered off to a marsh where it died of natural causes. According to Rabah, the guardian is exempt. He asserts that even according to those who maintain that one is liable in a case of "Techilaso b'Peshi'ah v'Sofo b'Ones," in this case one is exempt because the Malach ha'Maves could kill the cow just as easily whether it was at home or in the marsh, since it died naturally. Rabah's words are proof for the Riva's assertion, because Rabah maintains that the reason why the guardian is exempt is that there is no connection between the original Peshi'ah and the final Ones.

(b) The BA'AL HA'ME'OR (22b of the pages of the Rif) answers that although in all other cases the Halachah is that one is liable for "Techilaso b'Peshi'ah v'Sofo b'Ones," nevertheless the Torah makes a special exception in the laws of Bor.

The Ba'al ha'Me'or's source for this distinction is the Gemara later (53b). The Gemara there says that the two times the Torah says that the dead body of the animal damaged "will belong to him" are in connection with a Bor which damaged (Shemos 21:34) and a Shor that damaged (Shemos 21:36).

The Gemara asks that although the verse which mentions Bor is expounded to teach a leniency, the verse which mentions Shor is expounded to teach a stringency. How can the same verse have a lenient implication for Bor but a stringent implication for Shor? The Gemara answers that the verse likely teaches an exemption in the laws of Bor since we find that the Torah teaches another leniency in the laws of Bor -- that the owner of the Bor is exempt from liability for damages of vessels which fall into the Bor. Since the Torah exempts the owner of the Bor in one regard, it is likely that the Torah exempts him in another regard as well.

The Ba'al ha'Me'or adds that although in all other cases of "Techilaso b'Peshi'ah v'Sofo b'Ones" the owner is liable, for Bor there is a special exemption and the laws of Bor cannot be compared to the laws of other dorms of damages. (D. Bloom)