Resources for Nedarim 29
The גמרא discusses the concept of קדושה בכדי לא פּקעה. רבא אדא says קדושה is not פּקעה בכדי ever, אביי seems to hold it always is, and רבא holds קדושת הגוף is not פּקעה בכדי but קדושת דמים is. Everyone seems to agree that by marriage it is never פּקעה בכדי. The ר"ןin ד"ה ועולאsays that everyone also agrees by דיני ממונות that we say it is פּקעה בכדי. In other words, if you sell something to someone till I move to Brooklyn then once you move the land automatically becomes yours again. In קובץ הערות סימן נ"ו there is a yesodosdik סימן that discusses our סוגיא. רב אלחנן זצ"ל brings the אבני מילואים in סימן כ"ח אות נ"ג who brings the ר"ן in גיטין who quotes the רא"ה which seems to argue with what the ר"ן is saying here. The רא"ה writes that if ראובן sells שמעון a piece of land גוף ופּירות for one day, then ראובן gets to keep the land forever. This is because once the original ownership stops for a second its over forever. This is similar to the case of someone who divorces his wife for a day where we say once the קידושין stops it’s over forever. The רא"ה seems to be saying that the concept of קדושה בכדי לא פּקעה applies even to דיני ממונותas well. This would seem to be directly against our ר"ן in נדרים. רב אלחנן זצ"ל in אות ה explains that there are two types of מכירה לזמן. One is where you are retaining some ownership and you are just selling an item for a period of time. That is the equivalent of a קנין פּירות which will simply disappear after the appointed time. However, if you, as the רא"ה wrote, sell the whole item entirely (גוף ופּירות) for a day, then that ownership that you sold will not be פּקעה בכדי. This helps answer another question. The אבני מילואים, also brought by the קובץ הערות in אות י"ג asks from a גמרא in קידושין that the following: if you are מקדיש the leg of a קרבן, the whole animal becomes הקדש. However, if you are מקדש half a lady, the קידושין is not valid at all and we don’t say the קדושה takes over like it does by a קרבן. The גמרא explains that the חילוק is that the woman never agreed to have her whole self be מקודשת so it won’t work (דעת אחרת שאני). If so, why is it in our גמרא that if you say to a lady “today you are my wife and tomorrow you are not” that the קידושין is fully חל? Why don’t we say the lady never agreed to a full קידושין? According to the רא"ה there is no question. When the man said “today you are my wife” he meant you are my full wife so the קידושיןcan’t be פּקע בכדי, but if he said I want to marry half of you then he at no point had a full קידושין so it is not חל at all.
The מנחת שלמה discusses other types of קדושה. Can you have קדושת ישראל לזמן? In other words, can you be מגייר for today and go back to being a נכרי tomorrow? Perhaps if you pasken that קדושה is always פּקע בכדי then you can be undo your קדושת ישראל בכדי as well? The מנחת שלמה answers that it would not work because it would be a lack of קבלת המצוות and wouldn’t even be considered a Jew for today.
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