This week’s shiur discussed the question whether you can make a neder on a davar sh’lo bo l’olam-something which is not here. The Rambam in Hilchos Erachin (6:30-32) says that a neder on a davar sh’lo bo l’olam works and his rayah is from Ya’akov. Ya’akov promised Hashem that he would bring ma’aser from whatever Hashem would give him and later on at the end of the Parsha we find that Hashem calls that a neder. In Hilchos Mechirah (22:17) the Rambam also brings this halacha but he writes it a little differently. In Hilchos Erachin he writes “if a person says ‘I will give any fish that I catch to Hekdesh’ then it works”. In Hilchos Mechirah he writes “if a person says ‘I will give any animals born to Hekdesh’ or ‘Any animals born will be hekdesh’ then it works”. In Hilchos Mechirah he brings both a case of “I will give” and a case of “it will be”. In Hilchos Erachin he only brings the case of ‘I will give”. The Raavad in Hilchos Mechirah argues on the Rambam that only a case of “I will give” works but the other case of “it will be” does not work. The question is what are they arguing about and why does the Rambam only bring one case in Erachin and both cases in Mechirah?
There are a number of mehalchim in the achronim to explain this Rambam. Rav Moshe in the Dibros Moshe Nedarim (Siman 6 anaf 5,6) presents one explanation. He writes that there is a machlokes rishonim whether you can make a neder on a mitzvah. Can one make a neder to say ‘I will learn this perek’. A neder is usually an issur on a cheftzah so how can it apply to an action? The Ran holds you can’t and when the gemara says that you can make a neder to say ‘I will learn this perek’, it really means you are making a shevuah. Other Rishonim like the Ramban and Ritva hold the neder works. Rav Moshe explains that they learn this from tzeddaka. The gemara in Rosh Hashana says one can make a neder on tzeddakah, so if a neder on tzeddakah works so too a neder on a mitzvah will work. The Ran will tell you that neder on tzeddaka doesn’t work b’toras neder but rather we say the rule of “amiraso l’gavoah k’mesiraso l’hedyot” applies even to tzeddaka and not just hekdesh. Therefore, when you say you give it to tzeddaka it is like the ani made a kinyan on it.
Rav Moshe explains that this is the machlokes between the Rambam and Raavad. The Rambam holds a neder on tzeddaka works like a neder and therefore even on a davar sh’lo bo l’olam a neder can work. You can obligate yourself through a neder to bring something or make something tzedaka in the future. Even a loshon of “it will be tzeddaka” should work. The Raavad however will tell you that using the loshon of “I will give” is a loshon of neder. But saying “it will be” is not a loshon of neder but more lie a loshon of nedava and that only works through the din of “amiraso l’gavoah k’mesiraso l’hedyot” and that can not work on a davar sh’lo bo l’olam.