Li-ilui nishmas R' Chaim Ozer Dovid ben Bentzion Yaakov
Faygie was being pursued by two men, Moishe and Dovi. She had to decide between them. Her father was asked in shul by his benchmate who the lucky guy is. He answered "Moishe is the lucky guy. Dovi is marrying her".
The mishna says [Kiddushin 58b] that if a man gives a woman money and says marry me after 30 days, and someone else comes in the interim and marries her, she is married to the second chap [which would probably be the first time I have ever written the word "chap" when I didn't mean the Yiddish (hard "ch") word for "got it"].
But let us say that the second fellow DIED or DIVORCED her [some people understand quickly that this was not meant to be:-)] before the 30 days were up, is she now married to the first fellow?
The Ramban was מדקדק in the mishna that it doesn't say "אינה מקודשת לראשון" meaning that the second marriage doesn't automatically preclude the first marriage from taking place. So if he dies or divorces within 30 days, she is married to the first fellow.
The Rosh was flustered by this opinion. He asserts that the moment she receives kiddushin from the second fellow, she has retracted from her desire to be married to the first fellow. And even according to Reish Lakish in the gemara who maintains that she may not retract, because her words [of retraction] cannot nullify her earlier words - לא אתי דיבור ומבטל דיבור - nevertheless, even he would agree that a מעשה such as receiving kiddushin, can be מבטל a דיבור.
The Rosh proves this from the gemara [59b]. R' Yochanan tries to prove that a דיבור is מבטל a דיבור from the mishna in Trumos. The mishna says that if the owner of the fruits nullified the שליח he appointed before he separated the תרומה, it is valid. So we see that a דיבור [of retraction] can nullify a דיבור [of appointment]. The gemara answers that the Mishna is talking about a case where the owner of the fruits went ahead and separated תרומה before the שליח managed to do so which is a מעשה and not just a דיבור. So a מעשה can be מבטל a דיבור but a mere דיבור doesn't have the power to be מבטל an earlier דיבור.
So too, claims the Rosh, if she accepted money from a second man, which has the status of a מעשה, that has the power to nullify the דיבור of the first man. So even if she is widowed or divorced within 30 days - she does not go back to the first man.
When you look at this Rosh, you rub your eyes in wonder. Can he really be saying this???
Think about it!:-).
The case of תרומה is fundamentally different than the case of kiddushin. In the תרומה case, when the owner of the fruits separated תרומה, the fruits lose their טבל status! So OF COURSE the שליח may not separate תרומה anymore. But in the kiddushin case, after the second gentleman dies or divorces her, she is now completely free to marry "bachelor number one" [a term from an old silly-silly-silly game show one should never have watched]. So how can the Rosh compare the two cases?
Full disclosure: This was not my קשיא but that of Rav Aharon Kotler.....
He answers as follows: The mishna says אם עד שלא תרם ביטל אין תרומתו תרומה. If we are referring to a case where the fruits lost their טבל status, why use the word "ביטל"? It is not merely a ביטול of the שליחות but something much more - הפרשה is no longer possible by the שליח because of the earlier הפרשה of the owner.
Therefore , the Rosh understood something that you won't see in the Artscroll elucidation [unless there is a footnote that quotes this chiddush of Rav Aharon...]. The mishna means that after separating the תרומה he retracted and did שאלה on the הפרשה. No more הפרשה, back to טבל.... And yet nevertheless, the mishna says that because of the ביטול [as expressed by his מעשה הפרשה], the שליח may not be מפריש. So that is exactly parallel to our kiddushin case. In both cases there was a מעשה that was מבטל a דיבור and in both cases the earlier דיבור was still theoretically possible afterward. In the תרומה case, since he did שאלה, it is now possible for the הפרשה of the שליח to take effect and nevertheless it doesn't, because his מעשה was מבטל his דיבור. In the kiddushin case, the מעשה of receiving from the second man was מבטל the דיבור [or really מעשה/דיבור] of the first man and thus the first kiddushin is OFF.