- קידושין בדבר שלא בא לעולם – Ex. “Become married to me after I convert”
The next Mishnah teaches several cases of kiddushin performed with a woman who is not currently eligible to marry the man, but he stipulated it should take effect after she becomes eligible. If one says, “Become married to me לאחר שאתגייר – after I convert to Judaism,” or לאחר שתתגיירי – “after you convert,” or לאחר שאשתחרר – “after I am freed from slavery,” or לאחר שתשתחררי – after you are freed, or לאחר שימות בעליך – “after your husband dies and you are single,” or או לאחר שתמות אחותיך – “after your sister, my wife, dies, permitting you to me,” or לאחר שיחלוץ ליך יבמיך – “after your yavam performs chalitzah for you,” the kiddushin is ineffective in all these cases even after the event takes place, because kiddushin was impossible at the time (the future eligible status is a דבר שלא בא לעולם – thing that has not come into the world). The same applies to being mekadesh his friend’s future daughter. On Daf 63a, Rebbe Meir argues and says that kiddushin is effective in all the above cases.
- כל שבידו לאו כמחוסר מעשה דמי – Ex. Designating produce as terumah to take effect when picked
A Mishnah teaches that one cannot separate terumah on grain still attached to the ground. Rav Assi asked Rebbe Yochanan, if someone designates picked produce as terumah on attached produce, or the reverse, לכשיתלשו – to take effect when [the produce] is picked, and it was subsequently picked, is the terumah effective? Rebbe Yochanan answered: כל שבידו – Anything that it is one’s power to change, לאו כמחוסר מעשה דמי – is not viewed as missing the act required to change it. Because he can pick the produce at any time, he can declare terumah to take effect after it is actually picked. Several challenges to Rebbe Yochanan’s principle are addressed. Conversion is not considered “in his power,” because it requires the supervision of three Jews, which he cannot control. Even if someone his mekadesh his own maidservant, to take effect after he frees her (which is within his power), kiddushin is ineffective, because מעיקרא בהמה – originally, she is like an animal, השתא דעת אחרת – whereas now, when she is freed, she becomes an independent mind. This fundamental change renders her a דבר שלא בא לעולם even where he can effect the change. Rebbe Yochanan can agree that if one is mekadesh his wife to take effect after divorcing her, it is ineffective, because although he can divorce her, בידו לקדשה – is it in his power to marry her later? Her consent is required!
- The minimum stage for taking terumah, or marrying a fetus, according to Rebbe Elazar ben Yaakov
In a Baraisa supporting Rebbe Yochanan’s opinion, Rebbe Elazar ben Yaakov goes further and says one may even designate terumah before the grain reaches the stage of שליש – a third of its growth, to take effect after it reaches this stage and is picked. Clearly, he holds one may effect transactions on a דבר שלא בא לעולם (since it is not in his power to separate terumah currently). Rabbah says that Rebbe Elazar’s ruling only pertains to שחת – growths at the fodder stage, but the earlier "אגם" stage is too insignificant. Rav Yosef says his ruling even applies to אגם. The Gemara quotes Rav Chanina that although one cannot marry someone’s future daughter, אבל אשתו מעוברת דבריו קיימין – but if his wife is already pregnant, his words (i.e., kiddushin) are effective. According to Rabbah, this can only be כשהוכר עוברה – when her fetus is discernible (parallel to the "שחת" stage of grain), and according to Rav Yosef, even before the fetus is discernible (parallel to the "אגם" stage). In another version, they argue about what kind of a שחתcan be designated, and both would agree the fetus must be discernible to effect kiddushin.
