Zevachim 93 - 99
“Why? Let the positive commandment come and push off the negative commandment!”
This question on our daf is an illustration of a principle that is found many times in Shas called “asei doche lo ta’asei” — i.e., a positive commandment pushes off and overrides a negative commandment that exists in a certain case. Fulfillment of a mitzvah to do a specific act takes precedent over the consideration for the prohibition that normally forbids doing that act if no positive commandment would be involved.
So, what exactly is the question in our sugya? First we need to examine the positive and negative mitzvot here. The Torah teaches that it is forbidden to break a bone of the korban Pesach: “And don’t break a bone in it”. (Shemot 12:46) A beraita teaches: Rabbi Shimon ben Menasia says, “This Torah prohibition applies whether or not the bone has marrow in it.” (Tosefot explains that the basis for extending this prohibition to include even a bone with marrow, and not more narrowly applying it only to a case where the bone has no marrow.)
There is also a positive mitzvah to eat all of the meat of the korban Pesach in Shemot 12:8: “And you will eat the meat on that night.”
This leads the gemara to ask, “The positive mitzvah of eating the meat (including the marrow in the bones) should push off the negative mitzvah to not break the bone, and thereby permit breaking a bone, based on the rule of aseh doche lo ta’aseh? Why does Rabbi Shimon ben Menasia say that Torah law forbids breaking a bone of the korban Pesach even if there is marrow inside?”
The commentaries ask an interesting question on this line of reasoning. We are taught that the rule of aseh doche lo ta’aseh applies only when the aseh and the lo ta’aseh would occur at the same time. But, here the lo ta’aseh comes first, when he breaks the bone, and only afterwards is the aseh fulfilled, when he eats the meat inside.
Many answers are offered and there is much discussion regarding this topic in the writings of our great Torah scholars. One answer is that since the mitzvah to eat the marrow cannot be done with first breaking the bone, when the eater breaks the bone to get to the marrow he has already begun to fulfill the act of the mitzvah to eat all of the meat of the korban Pesach. Therefore, it is considered as if the aseh is being done at the same time as the lo ta’aseh. This explains how to understand the legitimacy of the gemara’s question. (Turei Even)
- Zevachim 97b