Resources for Yevamos daf 90

1.     The גמרא lists several מצוות דאורייתא that we don’t do because of a גזרה דרבנן which are considered שב ואל תעשה. Amongst the list is wearing a linen garment without ציצית. תוספות in ד"ה כולהו asks that not putting on ציצית on a linen garment should be considered קום ועשה because the act of putting on a garment without ציצית is a violation of the חיוב to put on ציצית! He answers that the חיוב really only starts once you are already wearing it. The קובץ הערות in סימן ס"ט has a long and fascinating piece on this תוספות and the concept of עקירת דבר מן התורה in general. He brings the שאגת אריה in סימן ל"ב who asks on תוספות’s premise that the act of putting on ציצית is a violation of ציצית as a קום ועשה. He argues that there is no איסור לבישה at all—there is only a מצוה to put on ציצית and violating that can only be done passively by not putting on the strings. In fact, according to the מרדכי, if its שבת and you have a four cornered garment without ציצית you are allowed לכתחילה to wear it since you aren’t allowed to make ציצית on שבת. That seems clear that there is no איסור לבישה. So the ביטול עשה  of not putting ציצית  on a linen garment should clearly be considered שב ואל תעשה. To answer תוספות, רב אלחנן ז"ל has a few חקירות: First, do we view something as קום ועשה when you perform an act which is מחייב yourself or do we only look at the actual violation which is בשב ואל תעשה? (For example, walking into the בית המקדש  on the שלש רגלים  without a קרבן and violating ולא יראו פּני ריקם ). Second, when חז"ל made a גזרה and exempted us from a מצוה, did they make it that the מצוה doesn’t exist at all or were they just adding a גזרה but the מצוה still exists מן התורה. Third, why is there a חילוק between whether an act is done בקום ועשה or בשב ואל תעשה in terms of whether חֽז"ל could make a גזרה against it? Is it because קום ועשה is more חמור than שב ואל תעשה or does שב ואל תעשה just mean that there is a battle between the מצוה of listening to the חכמים vs. the מצוה דאורייתא of say blowing שופר on שבת so we just do nothing? He explains that these three חקירות are all linked. If you hold that ֽ חֽז"ל didn’t remove theמצוה entirely, then the issue is just a clash of the מצוה דאורייתא of blowing שופר on שבת vs the מצוה דאורייתא to listen to the חכמים and we just say better not to do anything. In that case, then we would consider the act of being מחייב yourself by putting on a linen garment of four corners a קום ועשה that you shouldn’t do. If however חז"ל removed the מצוה entirely, then the difference between קום ועשה and שב ואל תעשה is how חמור it is, and in that case we would say that if the violation only occurs passively then they have the ability to remove it. Therefore, he explains that תוספות who said that putting on ציצית was קום ועשה must have held that the מצוה דאורייתא still exists even after the גזרה, in which case doing nothing is preferred. As such, the act of putting on the ציצית would be considered קום ועשה. רב אלחנן ז"ל clarifies that this discussion has nothing to do with the חיוב מלקות as that is certainly contingent on whether the actual violation itself was done with an action or not.

Regarding the issue of whether חז"ל completely erased the מצוה דאורייתא when they made a גזרה not do something or not, רב אלחנן ז"ל brings a תוספות in סוכה דף ג ע"א ד"ה דאמר לך that says that when the גמרא says that someone who violated the דין דרבנן of having a סוכה that doesn’t just fit their body but even fits their table, they aren’t even יוצא the מצוה דאורייתא. Similarly, רבינו יונה in the beginning of ברכות says that someone who davens קריאת שמע של ערבית after חצות when it is still nighttime is not even יוצא מדאורייתא because חז"ל forbade it. Other ראשונים disagree. He brings from רב חיים סאלוויציק זצ"ל that even if you hold the מצוה exists, you would still not say עשה דוחה ל"ת even מדאורייתא (as the case of סדין בציצית requires) since in practice you aren’t supposed to do the מצוה. Interestingly, רע"א in דו"ח מערכה ח says that if someone blew שופר on שבת they would be יוצא.

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