“You’re engaged to me with the peruta (small coin) that I’m handing you right now, but on the condition that I speak to the governor on your behalf.” Or he tells her, “I’m going to be a po’el (worker) for you for a day.” If he followed through—if he spoke to the governor on her behalf or worked for her as a worker—we say she’s mekudeshet, she’s engaged to him, and if not, she’s not engaged to him.
You may think, if you don’t have this Mishnah, that the woman could come and claim, “Oh, I wasn’t happy with what you did for me by speaking to the governor, or you didn’t work hard enough for me, and therefore not mekudeshet.” But you say, “No, no matter what, she has no right to complain about the quality of work that he did in terms of his intervention, speaking to the governor, or in terms of his working for her as a po’el.”
If someone tells a woman, “You’re engaged to me, but only under the condition that my father approves of this marriage,” then, if the father approves of the marriage and does not object during the stipulated time period, she is mekudeshet. But if the father does not approve and does object during that time period, we say she’s not engaged.
But if the father dies during that time period without objecting, then she is engaged because there’s no objection, and there can no longer be an objection, so therefore we say she’s married right away. But if the groom dies at that time, we tell the father that he should not approve of that marriage, because we want to make sure that the groom is not engaged and that the kiddushin (betrothal) does not kick in retroactively and does not take place. Therefore, the woman is always a single girl.
If she was married—if the father did approve of it—then you have a married girl who now dies childless, and she has to do yibum (levirate marriage) or chalitza (levirate release ceremony) with the groom’s brother. So we tell the father, “Nix this marriage; say you don’t approve of it,” so that the bride does not have to go with yibum or chalitza.