The gemara on 4a explains why we need limudim for both maase yadayim ( V'chi yimkor) and kesef kiddushin ( extra yud in Ayin vs an kesef) to teach that they accrue to the father based on the fact that kesef kidushin comes maalma and that maase yadayim may be in leiu of mezonos.
However, why do we need the drasha of Ayin at all since we have the sevara/drasha Es biti nasati. The sevara of aviha mekabel kidushin vyihi shaklah kaspa should explain why the father gets kesef kidushin for both a ketana and naara.
Gary Schreiber, Chicago, IL USA
Regarding the father's rights in his daughter: The Gemara on 3b confines the Pasuk "es Biti Nasati" to a Ketanah, who does not have a Yad, but precludes a Na'arah who does. Rashi explains that we will not even know that her father can be betroth her (let alone receive the money of her Kidushin).
The Gemara then suggests that we should learn a Na'arah from "bi'Ne'urehah Beis Avihah", which it rejects based on the fact that this Pasuk is confined to Nedarim.
And it concludes that we learn a Na'arah from the extra 'Yud' in Ein Kesef (and since the father receives the money, it is evident that he can betroth her as well).
Be'Virchas Kol Tuv