1) WITNESSES FOR THE APPOINTMENT OF A SHALI'ACH
QUESTION: Ravina rules that when a man is Mekadesh a woman to his son without his son's knowledge, the Kidushin does not take effect. The father has no right to be Mekadesh a woman to his son without the son's consent because the son is not in the domain of the father, and, moreover, because a man always checks his future wife meticulously before he marries her (RASHI 45b, DH Shema Nisratzeh). We do not assume that the son appointed his father as his Shali'ach to give the Kidushin because a son is not so brazen as to make his father his Shali'ach.
The ROSH proves from the Gemara that it is unnecessary to have witnesses present at the appointment of a Shali'ach to perform an act of Kidushin (a Shali'ach l'Holachah). Although the rule is that "Ein Davar sheb'Ervah Pachos mi'Shenayim" (any matter which involves a prohibited relationship requires the testimony of two witnesses), the appointment of a Shali'ach does not directly effect Kidushin, and therefore there is no need to have witnesses present to validate the appointment.
The RAMBAM (Hilchos Ishus 3:15) explains the proof of the Rosh from the words of the Gemara that says that "perhaps" he made a Shali'ach. If witnesses must be present at the appointment of a Shali'ach, what is the Gemara's doubt? Moreover, if witnesses were present who attest to the son's appointment of his father as his Shali'ach, why does the Gemara say that a son is not so brazen as to appoint his father as a Shali'ach for him? There are witnesses who testify that he was so brazen!
The Rishonim, however, rule (based on Gitin 63b) that a woman who appoints a Shali'ach l'Kabalah to receive Kidushin for her must do so in front of witnesses, apparently because the appointment of a Shali'ach is considered a "Davar sheb'Ervah." If her appointment of a Shali'ach requires witnesses because it is considered a "Davar sheb'Ervah," why does the man's appointment of a Shali'ach l'Holachah not require witnesses? (Indeed, the Rambam rules that the appointment of a Shali'ach l'Kabalah requires witnesses, and that the appointment of a Shali'ach l'Holachah does not require witnesses.)
ANSWER: RAV MOSHE FEINSTEIN zt'l (IGROS MOSHE EH 3:32:3) explains the difference between the appointment of a Shali'ach l'Holachah and the appointment of a Shali'ach l'Kabalah based on two factors. The first factor is the fundamental difference between the role of the man and the role of the woman in the act of Kidushin, which in turn affects the roles of their respective Shelichim. The second factor is exactly when a "Davar sheb'Ervah" requires two witnesses.
The active participant in the act of Kidushin is the man. The woman plays only a passive role. The Kinyan is executed by the man while the woman is the passive subject of the Kinyan. (See AVNEI MILU'IM, and RAN to Nedarim 30a.) In order for a Shali'ach to perform an act of Kidushin for the man, the man merely needs to appoint the Shali'ach as his agent to perform the act. The mere appointment as a Shali'ach empowers the Shali'ach to perform an act for the man. In contrast, in order for a Shali'ach to receive Kidushin for the woman, the Shali'ach must play a passive role. Since he performs no "act" (since the woman herself is passive in the act of Kidushin), the right to receive Kidushin must be transferred from the woman to the Shali'ach so that the Shali'ach can serve as her substitute.
The only situation in which a "Davar sheb'Ervah" requires two witnesses is when a change of status (or new status) takes effect. In every act of Kidushin and Gerushin, a change of status takes effect, and since the law of "Davar sheb'Ervah" in all other cases is derived from Kidushin and Gerushin, witnesses are necessary only in cases of "Davar sheb'Ervah" in which a change of status takes effect. The woman's appointment of a Shali'ach creates a new status. She transfers her power to the Shali'ach and gives the Shali'ach the new right to receive Kidushin in her place. The man's Shelichus, in contrast, does not require such a change of status or transfer of power. Rather, the Shali'ach functions on his own right and performs the act on behalf of the man through the Halachah of Shelichus. Since no new status is created by the appointment of the Shali'ach, the testimony of witnesses is not required.

45b----------------------------------------45b

2) THE CONSENT OF THE FATHER FOR THE KIDUSHIN OF HIS DAUGHTER
QUESTIONS: Ravina rules that when a man is Mekadesh a woman to his son without his son's knowledge, the Kidushin does not take effect (45a-45b). The father has no right to be Mekadesh a woman to his son without the son's consent because the son is not in the domain of the father, and, moreover, because a man always checks his future wife meticulously before he marries her (RASHI 45b, DH Shema Nisratzeh). We do not assume that the son appointed his father as his Shali'ach to give the Kidushin because a son is not so brazen as to make his father his Shali'ach.
The Gemara asks that perhaps the son expressed interest in marrying the woman, and thus the father may act on his own accord, in the capacity of Shali'ach for his son, to be Mekadesh the woman to him (RASHI). Why, then, is the Kidushin not valid? Rabah bar Shimi answers that Ravina explicitly states that he does not agree with Rav and Shmuel's ruling (that in the case of a Ketanah who accepted Kidushin without her father's knowledge, and her father's consent became known, the Ketanah's Kidushin takes effect), and thus the son's show of consent does not enable the Kidushin to take effect.
Based on Rabah bar Shimi's answer, most Rishonim rule that a Ketanah who accepts Kidushin without the knowledge of her father is not married and needs neither a Get nor Mi'un, because the Halachah does not follow the view of Rav and Shmuel and there is no concern that the father consented. (See RIF and ROSH.)
(a) However, the Gemara records an incident which seems to contradict the ruling of the Rishonim. The Gemara relates that a husband and wife were arguing whether to marry off their daughter to a relative of his or to a relative of hers. The wife persuaded her husband to agree to marry off their daughter to a relative of hers. At the Se'udah they made to celebrate the choice, a relative of the girl's father was Mekadesh the girl without the knowledge of the father. The Gemara questions whether the Kidushin made by his relative is valid or not. RASHI explains that the question is whether or not we assume that the father consented to the Kidushin. The Gemara concludes that we do not assume that he consented, either because a person does not give his word and then renege on it (as the verse in Tzefanyah 3:13 teaches) or because a man does not incur the expenses of a large Se'udah for nothing.
The Gemara implies that if not for the verse in Tzefanyah or for the logic that a man does not incur expenses for nothing, there would be a doubt about whether the Kidushin is valid or not. How is this to be reconciled with the ruling of the Rishonim that there is no concern that the father consented?
(b) Another question arises based on the next Sugya which discusses a Ketanah who accepted Kidushin with the consent of her father but then performed Nisu'in without his consent. The Gemara cites a dispute about whether there is concern that perhaps the father will object to the Nisu'in when he finds out about it. The Gemara implies that if the father consents to the Nisu'in when he finds out about it, the Nisu'in will be valid. Why is the Nisu'in valid if, at the moment it occurred, the father's consent was not present (since, according to the ruling of the Rishonim, we do not assume that he consented)?
(c) In the Gemara's case of a Ketanah who accepted Kidushin without the knowledge of her father and then performed Nisu'in without his knowledge, Rava explains that since the daughter acted rashly as though she were an orphan without a father, her father should have protested when he found out about the Nisu'in. His lack of protest implies that he agrees to the marriage. How is this consistent with Rabah bar Shimi's ruling that there is no concern that the father consented?
ANSWERS:
(a) The RIF answers that since the father originally expressed his desire that his daughter marry one of his relatives, the concern is not only that later the father will consent to the marriage, but that the father was an active partner in the "scheme" and told his relative explicitly to be Mekadesh his daughter. Accordingly, even Ravina agrees that the father's consent can make the Kidushin take effect.
(b) The same reasoning answers the second question. Since in this case the father originally consented to the Kidushin, we may assume that he agrees to the Nisu'in as well. Only when the father explicitly objects will this assumption be proven incorrect, but in lieu of his objection we rely on his original consent to the Kidushin. (See RASHBA.)
(c) The RAN comments that since the Rif does not record this case of the Gemara in his commentary, he apparently maintains that the Halachah does not follow the Gemara's ruling in this case. The only way in which the Kidushin could be valid is if the consent of the father makes it take effect retroactively, but this is contrary to the ruling of Rabah bar Shimi and the Rishonim.
The SEFER HA'MIKNAH and AVNEI MILU'IM (37:10) offer a different explanation which reconciles the ruling of the Rif with the words of the Gemara. The opinion expressed by the Gemara in this case is that of Rav Huna who maintains that Chupah alone is an effective form of Kinyan for marriage, even without Kidushin. Since the consent of the father can be verified after the Nisu'in, his consent does not need to work retroactively from the time of Kidushin in order for the Kidushin to take effect. Rather, his consent works at the time of the Chupah and shows that he is in favor of the act of Chupah which, according to Rav Huna, suffices to create the bond of marriage. Since the Rif rules that Chupah is not sufficient and that Kidushin is also necessary (not like Rav Huna), he does not rule in accordance with the Gemara. (A. Kronengold)