Resources for Nedarim 8
1. The גמרא says that if one makes a נדר or שבועה to do a מצוה it is not valid since he is מושבע ועומד מהר סיני. However, he is allowed to make such a נדר for the purpose of לזרורי נפשיה. There is a מחלוקת ראשונים which leads into a מחלוקת ﭏחרונים as to how not valid this נדר is. The ר"ן says that the concept of מושבע ועומד מהר סיני is only relevant to the need to bring a קרבן. This is because the דרשה on the פּסוק where we learn to exclude נדרי מצוה is talking about קרבן. However, the נדר is חל in regards to the לאו of לא יחל דברו. This is also the opinion of the בעל המאור. However, theרמב"ן in מלחמות in שבועות דף י"ג ע"ב בדפּי הרי"ף disagrees and says that a נדר to do a מצוה is not valid at all. He learns this from the פּסוק that says לא יחל דברו, which sounds like for his words he should not violate but he can violate for חפצי שמים. The קצות החושן in סימן ע"ג ס"ק ה asks how can it be that the נדר is not valid at all? The גמרא says you can make נדרי מצוה for the purposes of לזרוזי נפשיה. What kind of זירוזis there if its completely not valid? Rather, the קצות concludes that even according to the רמב"ן there is an איסור, just not the full לאו of בל יחל with מלקות. As a support to this, he brings the טור in יו"ד סימן רל"ו who says “there are some שבועות that one does not need to bring a קרבן for violating but there is still an עברה anytime he is משקר בשבועתו”. We see one can still have the עברה even though it is not the full עברה. The אפיקי ים inחלק א סימן ל"ו disagrees with the קצות. He says that according to theרמב"ן there is no חלות whatsoever. As to the question of the קצות that if there is no איסור then how is there any זירוז נפשיה, he explains based on the ריטב"א, מאירי, and other ראשונים that the גמרא means to be say with that by making this שבועה he has not violated making a שבועת שוא (a pointless שבועה) because a person will take his own words and self imposed שבועה seriously (even though it isn’t valid) and will therefore do what he says (hence the זרוזי נפשיה). The מאירי adds another point explicitly (which may also be the opinion of the ריטב"א ): if the person ends up violating what he said, he is retroactively עובר having made a שבועת שוא (because he obviously doesn’t take his words seriously so there was no point)! This is how the אפיקי ים explains the טור as well. Anyone who violates their שבועה על המצוות gets an עברה but not of שבועת שקר but rather of שבועת שוא. He also says that this is the opinion of the רמב"ם in הלכות שבועות פּרק ה׳ הל׳ ט"ז who says almost מפורש like the מאירי.
2. The גמרא says that someone who says they will learn פּרק זה has made a נדר גדול לאלקי ישראל. The גמרא then asks that this should not be a good נדר because he is מושבע ועומד מהר סיני. There is a fundamental question asked by many ראשונים ואחרונים: there is no מצוה need to learn פּרק זה! There is no greater חיוב to learn the first פּרק of נדרים any more than there is to learn the second פּרק. So why can’t the נדר be חל in terms of which פּרק I must learn? The ריטב"א’s example is: if a person swore to eat bread today and then swore to eat this particular piece of bread today, would the second שבועה not be חל? The ריטב"א therefore explains that this is exactly what the גמרא’s answer is! When it said אי בעי פּטר נפשיה בקריאת שמע שחרית וערבית, it meant he could have learned something else (meaning קריאת שמע is just an example of a piece of תורה), so the נדר is חל in terms of which פּרק he must learn.
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