As we have learned, in order to create a marriage, a man must give a woman an object of value and say, “Harei at mekudeshet li be-kesef zo ke-dat Moshe ve-Yisra’el – behold with this money you are betrothed to me according to the laws of Moses and Israel.” What if he offered to provide the woman a service that had value? Would that suffice to act as money?
From a simple reading of our Mishna, it would appear that services performed on the woman’s behalf can be used for marriage. The Mishna teaches that if a man says, “Harei at mekudeshet li al menat she-adaber alayikh la-shilton – behold you are betrothed to me on the condition that I speak to the governor on your behalf,” the marriage will take place. This assumes, of course that he fulfills the condition. The Rambam says that simply speaking to the governor is not enough; he must successfully petition the governor on her behalf. The Rosh argues that all he agreed to do was to argue her case, implying that if he did so properly the marriage would come into being, since representing her has value (i.e. she would have had to pay someone to do it) even if he is unsuccessful.
This halakha notwithstanding, Reish Lakish limits the rule of the Mishna to a case where the man not only performed the service, but also gave the woman money separately. He argues that the author of the Mishna does not believe that payment for a service is due only at the end, rather he believes that payment is essentially due from the beginning of the service until the end, so that when the service is completed the person who contracted the service – who really should have been paying throughout – has a standing debt to the person who performed the service. Since we have learned (see Massekhet Kiddushin 47) that a man cannot marry a woman simply by forgiving a debt that she owed him, the kiddushin will not work unless he actually gives her something of value.