1) THE STATUS OF "KINYAN KESEF"
QUESTIONS: The Gemara teaches that even if Kesef is not a valid Kinyan mid'Oraisa, the Chachamim instituted that a person who wants to retract from a purchase for which he has already paid must receive the curse of "Mi she'Para." This curse effectively prevents a person from retracting from a purchase once he has given the money to the seller.
RASHI (DH Kai) asks that according to this reasoning, what difference does it make whether Kinyan Kesef is mid'Oraisa or not? Even if Kinyan Kesef is not Koneh mid'Oraisa, a person may not retract from a purchase that was done with Kinyan Kesef! (Rashi may be following his opinion expressed elsewhere. Rashi always defines "Kinyan" to mean that a person may no longer retract from the agreement. See Gemara 45b, and see Rashi to 45a.)
Rashi answers that the practical difference between whether or not Kesef is Koneh mid'Oraisa is with regard to Isurim. For example, "if a person used it to be Mekadesh a woman," according to Rebbi Yochanan (who says that Kinyan Kesef is valid mid'Oraisa) the Kidushin is valid, and according to Reish Lakish the Kidushin is not valid.
There are a number of important questions that may be asked on Rashi's explanation.
(a) Rashi implies that it is difficult to find a practical difference between the views of Rebbi Yochanan and Reish Lakish. There seem, however, to be a number of obvious differences which Rashi could have mentioned which are discussed explicitly in the Gemara.
1. The Gemara mentions several times that in unusual circumstances, Kesef is Koneh according to Rebbi Yochanan, since the Chachamim did not annul the Kinyan Kesef in situations which are very uncommon. For this reason, according to Rebbi Yochanan, a Kinyan Kesef takes effect when a person is Koneh a cow with the "price," or value, of an ox (meaning the money that he owes for the purchase of the ox) (46b), and a Kinyan Kesef takes effect when a person purchases an object with a lump sum of money and does not show concern about the exact amount (47a). Also, the Gemara (49b) teaches that when the merchandise purchased with Kesef is in the buyer's attic which is rented to the seller, the Kinyan takes effect right away because the buyer will protect the merchandise there since it is in his property (and there is no need to enact that Kinyan Kesef will not work in order to encourage the seller to save the merchandise). In all of these cases, the Kinyan is not valid according to Reish Lakish, but it is valid according to Rebbi Yochanan. (PNEI YEHOSHUA, MAHARAM SHIF. The RITVA indeed suggests that these are the practical differences between the views of Rebbi Yochanan and Reish Lakish.)
2. The Gemara later teaches that when a person pays money of Hekdesh to purchase food, according to Rebbi Yochanan he is liable for Me'ilah since the Kinyan takes effect mid'Oraisa, while according to Reish Lakish he is not liable for Me'ilah. (PNEI YEHOSHUA)
3. Rashi earlier (47b, DH Kach Tiknu) writes that if the buyer sees a fire approaching the merchandise for which he paid but which he did not yet take, he is able to retract from the purchase. Rashi's words imply that he agrees with the view of the BA'AL HA'ME'OR who rules that after the merchandise is destroyed, it is too late for the buyer to back out of the deal, according to Rebbi Yochanan. The loss must be suffered by the buyer since he was already Koneh the merchandise with Kinyan Kesef. Although the Chachamim said that a Meshichah must be done in order to finalize the purchase, they did not revoke the Kinyan Kesef. Rather, they instituted that even after the Kinyan Kesef, the buyer may retract while the merchandise is still in existence, as long as he did not do Meshichah. (See Insights to 47b.)
Accordingly, there is an important practical difference between Rebbi Yochanan and Reish Lakish. When the merchandise is destroyed before the Meshichah is done, according to Reish Lakish the loss is suffered by the seller, since the buyer never made a Kinyan on it. According to Rebbi Yochanan, the loss is suffered by the buyer, since he did make a Kinyan (with Kesef) but did not take advantage of the Takanah d'Rabanan that allowed him to retract from the Kinyan. (MAHARAM SHIF)
4. Another practical difference is the type of Kinyan that a Nochri may use to acquire an object. The Gemara in Bechoros (13a) teaches that whatever Kinyan the Torah prescribes for Jews, the opposite type of Kinyan must be used by a Nochri. Therefore, according to Rebbi Yochanan a Nochri can be Koneh only with Meshichah. According to Reish Lakish, a Nochri can be Koneh only with Kesef (the Chachamim did not change the Kinyan of a Nochri).
(b) Why should the Kidushin be valid according to Rebbi Yochanan? If the Chachamim annulled Kinyan Kesef, then the rule of "Hefker Beis Din Hefker" should be applied to teach that the object does not belong to the buyer even though he made a Kinyan Kesef. If he uses it to be Mekadesh a woman, it should not be valid, since the Chachamim removed it from his possession! (RITVA)
ANSWERS:
(a) Perhaps Rashi does not mention these other practical differences between the views of Rebbi Yochanan and Reish Lakish for the following reasons:
1. Rashi does not mention the cases which are not common because he wants to give a common practical difference. Perhaps the case in which the attic belongs to the buyer and is rented to the seller is also not common enough for Rashi to mention it. (MAHARAM SHIF)
Another possibility is that Rebbi Yochanan and Reish Lakish (on 47b) are arguing about the statement of the Mishnah (44a), "Keitzad... Nasan Lo Ma'os...." Since the Mishnah states that the Kinyan is not valid, it obviously is not discussing any of the cases in which Rebbi Yochanan maintains that the Kinyan Kesef is valid.
2. Rashi does include Me'ilah as one of the practical differences between Rebbi Yochanan and Reish Lakish. This is what he means when he writes that the difference between them is with regard "to Isurim." He mentions Kidushin only as one example of an Isur, which can be derived from the Gemara's statement that the Isur of Me'ilah is a practical difference. (Rashi prefers Kidushin to Me'ilah as a practical difference because it applies even today, while objects subject to Me'ilah today are rare.)
3. Rashi wants to mention as a practical difference a case in which Reish Lakish would says that the Kinyan is not valid and "Mi she'Para" will not apply (as mentioned above in the question). When Rashi writes that the buyer may retract when he sees a fire approaching the merchandise, he means that the buyer is not bound even by "Mi she'Para" to continue with the deal, as TOSFOS says (47b, DH Iy). Since the buyer will suffer a significant loss by not retracting from the purchase, "Mi she'Para" does not apply. Perhaps Rashi maintains that after the merchandise is destroyed, "Mi she'Para" would apply, since the buyer -- by retracting -- will cause the seller a significant loss. It is only while the fire is approaching that he is permitted to retract, in order to motivate the seller -- who becomes the owner when the buyer retracts -- to do whatever he can to prevent the fire from harming the merchandise.
4. The PNEI YEHOSHUA writes that Rashi indeed could have mentioned the difference of whether a Nochri is Koneh with Meshichah or with Kesef.
Alternatively, Rashi might follow the opinion of RABEINU CHAIM HA'KOHEN (cited by Tosfos to 48b) who suggests that according to some Amora'im Kesef is Koneh for both a Jew and a Nochri.
Finally, the suggestion mentioned earlier (in answer 1 above) that Rashi wants to give a practical difference which applies to the case written in the Mishnah (44a) will also answer why Rashi does not mention the practical difference of how a Nochri is Koneh.
(b) The Acharonim suggest a number of reasons for why Rashi does not apply the rule of "Hefker Beis Din Hefker" with regard to a purchase made with Kinyan Kesef.
1. The AVNEI MILU'IM (28:33) writes that according to Rashi, a Kinyan instituted by the Chachamim is not recognized on the d'Oraisa level. Consequently, with regard to Kidushin (which involves the creation of an Isur d'Oraisa), we are concerned only with who owns the object from a d'Oraisa point of view. Even though the Chachamim enacted that the buyer may back out of the purchase through "Hefker Beis Din Hefker," they cannot actually remove the object from the owner's possession. This means that through "Hefker Beis Din Hefker" the Chachamim do not actually transfer the ownership of the object, but rather they instituted that it is to be treated as though another person owns it.
A question on this approach may be asked from the fact that Rashi does not mention as a practical difference a case in which the buyer did Meshichah but did not pay money. According to the Avnei Milu'im, in such a case Rebbi Yochanan and Reish Lakish would disagree; according to Rebbi Yochanan the Kidushin would not be valid. (See TESHUVOS MAHARIL DISKIN #5.) The answer might be that Rebbi Yochanan would agree that the Kidushin takes effect mid'Rabanan in such a case.
2. The MACHANEH EFRAIM (Kinyan Ma'os #11) and REBBI AKIVA EIGER explain that Rashi does not mean that the buyer may be Mekadesh a woman with the merchandise, according to Rebbi Yochanan. Rather, he means that the seller may be Mekadesh a woman with the money that he receives, according to Rebbi Yochanan. This is the way the TUR (CM 198) records this practical difference of Kidushin. Although our text of Rashi says that he "used it" for Kidushin, implying that the buyer used the merchandise, the RITVA cites Rashi as saying that he "used them" for Kidushin (i.e. the money), and he explains (like Rebbi Akiva Eiger) that the seller used the money for Kidushin in the case Rashi mentions.
Rashi may understand that the Chachamim indeed removed the merchandise from the possession of the buyer through "Hefker Beis Din Hefker." However, they did not remove the money which the seller received through "Hefker Beis Din Hefker," and they left it in his possession. Such an opinion is cited by TOSFOS (43a, DH Mai).
The Avnei Milu'im also mentions this possibility. (He does not accept that this is the opinion of Rashi, because the words of Rashi imply otherwise. Others, however, understand the words of Rashi differently and say that this is the opinion of Rashi.)
3. As mentioned above (a:3), Rashi maintains that the Chachamim did not revoke the Kinyan that takes effect with Kinyan Kesef. They instituted only that the buyer has the ability to revoke the Kinyan if he wants, as long as he has not yet done Meshichah. According to this opinion, it is clear that the Chachamim did not apply "Hefker Beis Din Hefker" to a Kinyan Kesef, and therefore the Kidushin will be valid.
Proof for this approach may be inferred from what the Gemara says about Me'ilah. The Gemara teaches that when a person pays money of Hekdesh to purchase food, according to Rebbi Yochanan he is liable for Me'ilah since the Kinyan takes effect mid'Oraisa, while according to Reish Lakish he is not liable for Me'ilah. If the Chachamim instituted that "Hefker Beis Din Hefker" removes the money from the possession of the seller, then the buyer should not transgress the Isur of Me'ilah when he gives the money to the seller, since the Chachamim did not let the seller acquire the money. (PNEI YEHOSHUA)
In fact, Tosfos in Avodah Zarah (63a, cited by MAHARAM here) indeed suggests that according to Rebbi Yochanan the buyer will not be liable for Me'ilah for this reason, according to the Gemara's conclusion.
In defense of the Rishonim who maintain that the seller does not retain ownership of the money (see beginning of Tosfos to 43a), one must explain that the Chachamim were Mafkir the money only after the seller took possession of it. They could not have been Mafkir it in a way that would prevent the seller from taking possession of it in the first place. (A similar concept may be found in Tosfos to 12a, DH Im Amart.) Therefore, the buyer transgresses the Isur of Me'ilah according to Rebbi Yochanan because of the brief moment at which the seller does own the money.
2) MAKING A "KINYAN" THROUGH THE FORGIVING OF A LOAN
QUESTION: Rava cites proof for the opinion of Reish Lakish from the verse of Shevu'as ha'Pikadon. The omission of the words "Tesumes Yad" implies that even when the borrower designates an object towards the repayment of the loan, if the lender does not do Meshichah on that object the borrower will not be liable to make a Shevu'as ha'Pikadon for denying the loan. This is because one is liable to make a Shevu'as ha'Pikadon only when he denies a specific object. Since Kesef is not Koneh, the object that was designated for the lender does not become the property of the lender until he does Meshichah.
It is clear from the Gemara that according to Rebbi Yochanan, the lender would acquire the object that was designated in place of the money that the borrower no longer needs to pay.
How can the lender acquire an object with Kinyan Kesef in such a manner? As mentioned earlier (see Insights to 46b), the Gemara teaches that a person cannot make a Kinyan Kesef through the pardoning of a loan ("Mechilas Milveh"). Rather, he must actually hand over money. Since the Gemara is discussing a case in which the borrower owes money to the lender, the lender should not be able to acquire with Kinyan Kesef what the borrower designates for him if he forgives the loan. (RAMBAN and Rishonim)
(According to the RAMBAM (cited in Insights to 46b) who writes that a Kinyan Kesef may be made with Mechilas Milveh, the Gemara is easily understood. According to the other Rishonim (cited in Insights there) who maintain that a Kinyan Kesef cannot be made with Mechilas Milveh, the Gemara is difficult to understand.)
ANSWER: The Rishonim answer that the verse implies that no Shevu'as ha'Pikadon is made, even when the borrower designates an object at the time that he receives the loan. At that time, a Kinyan Kesef can be made since the money is handed over to him at the same time that he gives the object to the lender in return for the money.
3) "ME'ILAH" WITH MONEY PAID FOR A SERVICE
QUESTION: The second proof that Rava cites for the opinion of Reish Lakish is from the Mishnah in Me'ilah (20a). The Mishnah teaches that when a person gives money of Hekdesh to a bathhouse attendant for the use of the bathhouse, he is liable for Me'ilah. This implies that when he gives money to purchase any other object he is not liable for Me'ilah, since Kesef is not Koneh mid'Oraisa. It is only when he gives the money to a bathhouse attendant that the money is Koneh. This Mishnah is proof for Reish Lakish who maintains that the Torah authorizes only Meshichah as a valid Kinyan for Metaltelin, but not the giving of Kesef.
If, mid'Oraisa, Kesef is not Koneh according to Reish Lakish, then why is a person liable for Me'ilah when he gives money to a bathhouse attendant? Kesef should not accomplish a Kinyan in any case.
ANSWERS:
(a) TOSFOS (DH Balan) explains that the money is given to the bathhouse attendant in order to rent the use of the bathhouse. Since the bathhouse is attached (Mechubar) to the ground, it is treated like land which can be acquired (or rented) mid'Oraisa with Kesef, even according to Reish Lakish.
RASHI (DH l'Balan), however, writes that the money is paid to the attendant in order to hire the attendant to wash him. Rashi clearly does not accept Tosfos' understanding that the money is being paid for the use of land.
(b) The RITVA explains that according to Rashi the money is a payment for the attendant's services after the bathing was finished. The Halachah is that money paid for hiring a worker must be paid only after the job is completed. At that time, the hired worker certainly is Koneh the money for the services that he rendered.
However, Rashi (DH Davka) writes that the money paid to the attendant is paid before the attendant does any work. The payment prevents him from retracting from the deal. The MACHANEH EFRAIM (Sechirus Po'alim #3) writes that it is evident from Rashi that although the wages of a hired worker must be paid only when the work is finished, nevertheless if the worker is paid before the work is done the money accomplishes a Kinyan and the worker cannot retract. (Although a worker (Po'el) who is hired for a specific amount of time may retract at any time, a Kablan who is hired for a specific task cannot retract.)
It is not clear, according to the explanation of the Machaneh Efraim, how Kesef accomplishes a Kinyan according to Reish Lakish if there is no Kinyan Kesef mid'Oraisa for Metaltelin.
Perhaps the Machaneh Efraim means that a hired worker has the status of an Eved, and Rashi maintains that even an Eved Ivri is comparable to Karka and can be acquired with Kesef. This is the opinion of the RAMBAM (Hilchos Mechirah 13:15). This seems to be the opinion of Rashi in Kidushin (28b; see Insights to Kidushin 28:1).
(c) The MORDECHAI (#301) cites the RI of VIENNA (the OR ZARU'A) who infers from the Gemara that even Reish Lakish agrees that Kesef acquires mid'Oraisa in a situation in which Meshichah cannot be done (since there is nothing to pull). When a person hires a worker who has tools, he can do Meshichah on the tools in order to make a Kinyan. When he hires a bathhouse attendant who works without tools, Kesef is Koneh.
This seems to be the intention of Rashi (DH Davka). This is also the opinion of TOSFOS in Bechoros (13b, DH Devar Torah), who writes that for this reason Reish Lakish maintains that Kinyan Kesef is effective for the redemption of Hekdesh. Meshichah cannot be done to take an object away from Hekdesh, because wherever the object is, it is in the domain of Hekdesh. That is why the Torah allows Kinyan Kesef to be used to redeem Hekdesh. (See PRI YITZCHAK 1:47.)
Similarly, the Ri of Vienna infers from here that according to Rebbi Yochanan, Meshichah is a valid form of Kinyan mid'Oraisa when it is not possible to acquire with Kesef, such as in the case of an object of Hefker, or a gift (in which case no money is given). This is also the opinion of TOSFOS in Bechoros (13a, DH mi'Yad). (However, the RAMBAN here argues and writes that even a gift or Hefker cannot be acquired through Meshichah according to Rebbi Yochanan, but must be acquired through Kinyan Chatzer.)

48b----------------------------------------48b

4) A SECURITY FOR THE PURCHASE OF A FIELD
QUESTION: Rebbi Yosi teaches in a Beraisa that when a person gives a security ("Eravon") to a seller for the purchase of a field and says, "If I retract from the purchase, you can keep the security, and if you retract, you will have to pay me twice its value," the conditions must be kept (because "Asmachta Kanya"). Rebbi Yehudah argues and says that the security acquires only the amount of the field that corresponds to the value of the security.
Raban Shimon ben Gamliel says that this dispute applies only when the buyer says, "Ervoni Yakun" -- "let my security acquire." When, however, a person submits a partial payment for the purchase of a field, everyone agrees that he is Koneh the entire field with that payment.
It is clear from the words of Raban Shimon ben Gamliel that the security mentioned in the first part of the Beraisa does not refer to an object given as a down payment for the field, and that is why it acquires only a corresponding value of the field. For what purpose, then, was it given? RASHI (DH bi'Zman) explains that it was given not as a partial payment but as a symbolic act of Kinyan which was intended to consummate the Kinyan on the entire field. Since the Torah does not consider such an act to be a Kinyan, it is not Koneh the field.
If the security was not given in a manner of Kinyan, then why does it acquire even an amount of the field equal to the value of the security? It should not acquire any of the field! (This question is included in the question of TOSFOS DH Echpol.)
ANSWERS:
(a) RASHI (DH Daiyo) implies that in fact a security is not Koneh anything for the buyer. Rather, the part of the condition that the buyer made which is not an "Asmachta" must be honored. Therefore, if either the buyer or seller retracts, then the other party may take an amount equivalent to the value of the security from either the field (if the seller retracts) or from the security (if the buyer retracts).
Other Rishonim do not accept this explanation because Rebbi Yehudah says that the security is Koneh, which implies that it consummates the sale (of the amount of land that corresponds to the value of the security). Perhaps Rashi was not bothered by the usage of the word "Koneh," since Rashi always translates the word "Koneh" to mean that neither party may retract from the deal (see beginning of Insight 48:1, above), and in the case of the security neither party may retract (for doing so will not save him from buying or selling at least the amount equal to the value of the security).
(b) The RITVA explains that "Ervoni Yakun" means that the security does not cause any Kinyan to take effect now, but rather that it should make a Kinyan take effect if one of the parties retracts. Since the buyer does not specify that he wants to make a Kinyan now, the security is not Koneh the field for him.
The Ritva asks why the security should be Koneh even part of the field, and he answers that although the buyer does not specify that he wants any Kinyan to take effect now, we may assume that he wants to be Koneh now at least an amount equal to the value of the security, in order to prevent both himself and the seller from retracting from the sale of that amount. (This is not similar to a down payment, because here it is assumed that the buyer specifically wants to acquire only part of the field and not the entire field.)
(c) TOSFOS (DH Echpol, DH bi'Zman) explains that "Ervoni Yakun" means that the buyer does want the security to acquire for him part of the field now. The security does not acquire for him the entire field because the words "Ervoni Yakun" imply that he wants to acquire part of the field that is worth twice the value of the security; he is saying that he wants "the security to acquire an amount equivalent to the value of the security, plus an amount equivalent to the value of the security." According to Rebbi Yehudah, since an "Asmachta" is not Koneh, the security can acquire only an amount equivalent to its value, but not more. (This is not similar to a down payment, because here the buyer specifically wants to acquire only part of the field and not the entire field.)
It is evident from the words of Rashi here (and on 45b, DH Matbe'a) that a Kinyan Kesef may be performed only with funds that are transferred for the sake of covering the cost of the field. A number of Acharonim explain that Tosfos (DH bi'Zman) argues with Rashi because he maintains that the Kesef does not have to be given specifically towards the cost of the field, but it can be given symbolically in order to effect the Kinyan (EVEN HA'AZEL, Hilchos Mechirah 1:4; CHIDUSHEI REBBI SHIMON SHKOP, Kidushin #3). However, according to the above explanation, Tosfos is rejecting Rashi's approach for a different reason (because of the original question: if the security was not given in a manner of Kinyan, then why does it acquire even an amount of the field equal to the value of the security?). Tosfos agrees that the money must be given for the purpose of paying for the cost of the field. Accordingly, this is the source for the ruling of the S'MA (CM 190:1) who writes that the Kinyan Kesef must be done with money paid specifically for the purchase.
The TAZ there argues and cites two proofs that the money does not have to be given with the intent that it cover the cost of the purchased item. His first proof is from the Gemara here that says that when the buyer says "Ervoni Yakun," the security acquires an amount of the field equivalent to the value of the security (according to Rebbi Yehudah), even though it was not given specifically as payment for part of the field. However, according to the above explanation, this is not a proof.
The Taz's second proof is from the Kidushin of a woman. Obviously, a man does not pay a Perutah to a woman in order to cover any "cost" of the woman, and yet the Kinyan of Kidushin is learned from the Kinyan of a field (Kidushin 2a). It must be that just as the Kinyan Kesef of Kidushin involves merely a symbolic act of handing over money, so, too, the Kinyan Kesef of a field involves merely a symbolic act of handing over money.
Perhaps this proof may be refuted as follows. When a person hires a worker, even though the money that he pays to the worker does not correspond to the value of the worker himself, it does correspond to the value of the service that the worker performs. Similarly, the Kesef paid to the woman is paid for the Shibudim that the woman accepts upon herself to do for her husband in her role as his wife.
One might ask, however, that the husband gives only a Perutah, and what the woman does for her husband is certainly worth much more. The answer is that Rashi here writes that the money needs to be given only as "Techilas Pira'on," the first installment of the payment. In the case of Kidushin, the Perutah is the first installment, and the rest is paid through the obligations that the husband accepts to do for his wife in his role as husband. (M. Kornfeld)