2) KIDUSHIN PERFORMED WITH "MEI CHATAS" OR "EFER PARAH"
OPINIONS: The Gemara states that when a man is Mekadesh a woman by giving her Mei Chatas or Efer Parah, the Kidushin is valid. The Rishonim disagree about the details of cases of Kidushin performed with Mei Chatas or Efer Parah, according to the Gemara's conclusion.

(a) RASHI apparently understands that the man is Mekadesh the woman with the money she owes him for his labor. The Mishnah refers to a case in which the woman was Teme'ah and needed Mei Chatas to become Tahor, and the man purchased it on her behalf. Since he is permitted to take payment for his services, the woman owes him that amount. When he pardons her debt she becomes Mekudeshes to him.

(b) The RASHBA disagrees with Rashi for two reasons. First, according to Rashi's understanding, the case of the Gemara is a case of "Mekadesh b'Milvah," wherein the man forgives a debt which the woman owes him and says that she should become Mekudeshes to him with the debt. The Gemara (6b, 47a) teaches that such a Kidushin is not valid. In order for this case not to be a case of "Mekadesh b'Milvah," Rashi would have to rule that "Sechirus Einah Mishtalemes Ela ba'Sof" -- the money owed for labor rendered becomes a debt only after the conclusion of the work (and thus the woman does not really owe any money to the man at the time he is Mekadesh her). This, however, is the subject of dispute (see earlier, 47b).

Second, the Mishnah states, "One who is Mekadesh with Mei Chatas or with Efer Parah...," which implies that the man uses the actual item (and not the value of services rendered to obtain the item) to be Mekadesh the woman.

The Rashba explains instead that since one may use the Mei Chatas to earn money (by delivering the Mei Chatas ("Hava'ah") for the procedure of Haza'ah), it has some monetary worth. When the man gives it to the woman, it is considered as though he gives her something of monetary value since she, too, could have performed the same service and received the same fee.

3) A SHALI'ACH WHO BETROTHED A WOMAN TO HIMSELF
QUESTION: The Mishnah teaches that when one man appoints his friend as a Shali'ach to be Mekadesh a woman for him and the Shali'ach goes and is Mekadesh her to himself, the Kidushin takes effect with the Shali'ach (and not with the sender).

In the Mishnah's case, the woman must be aware that the Shali'ach intends to be Mekadesh her to himself and not to the sender, because otherwise the Kidushin clearly would be a Kidushei Ta'us (Kidushin accepted in error). Why, though, does the Mishnah need to teach that the Kidushin with the Shali'ach takes effect? Since she has intent to marry the Shali'ach and the Shali'ach has intent to marry her, it is obvious that the Kidushin with the Shali'ach takes effect.

ANSWERS:
(a) TOSFOS explains that the Mishnah refers to the following scenario. When the Shali'ach met the woman, he introduced himself as the Shali'ach for the man who appointed him. Before he gave her the money of Kidushin, he changed his mind and decided to be Mekadesh the woman for himself. One might have thought that when he pronounces, "Harei At Mekudesh Li" -- "You are hereby Mekudeshes to me," he still acts on behalf of the man who sent him; he uses the word "Li" ("to me") in his capacity as a substitute for the man who appointed him. The Mishnah teaches that he is assumed to refer to himself when he uses those words.

(b) The RASHBA and RITVA explain that in the case of the Mishnah, the Shali'ach did not inform the woman that he was appointed by the sender. (They infer this from the fact that the Gemara calls his act "trickery.") If the woman would have known that someone else was interested in being Mekadesh her, perhaps she would not have agreed to the Kidushin of the Shali'ach and his Kidushin should be considered a Kidushei Ta'us and not take effect. The Mishnah teaches that the Kidushin is not a Kidushei Ta'us and it indeed takes effect.

(c) Alternatively, one might have thought that since the Shali'ach acted improperly (with an act of "trickery," as the Gemara calls it), the Rabanan nullified the Kidushin as they did in other cases of Kidushin made improperly. Therefore, the Mishnah teaches that in this case the Kidushin indeed takes effect.