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Facing The Consequences
‘Uncleanness Is Retroactive!’
(Nazir 16a)



Our daf pursues discusses whether one has fulfilled certain obligations, such as offering the paschal sacrifice, despite contamination occurring later on that same day. This question requires further deliberation.


Pesik Reisheih – A Beheaded Chicken

The Gemara (Shabbos 41a-46b) stresses that R. Shimon’s lenient position does not apply to cases of pesik reisheih. The term pesik reisheih – lit., “if its head is cut off” – is a colorful expression borrowed from the ritual slaughter of chickens. One cannot justifiably cut off a chicken’s head and then claim that one had no intent to kill it. “If its head is cut off, will it not die?” the Gemara asks rhetorically. This expression is used to describe the inevitable consequence of an action. One cannot use the excuse of davar she’eino mis’kaven – that it was the unintentional result of an action that might not be forbidden on Shabbat; such actions are forbidden even by R. Shimon.

  1. Shimon, for example, agrees that this is forbidden to drag a bench across a dirt floor if the bench is so heavy that it will certainly create a furrow. Similarly, R. Shimon agrees that it is forbidden to close a door or window if doing so will trap an animal inside the room. Although one may not have intended to trap the animal, it was inevitable – a pesik reisheih – that the animal would be trapped by his action.


A Retroactive Pesik Reisheih

The intriguing question of a “retroactive pesik reisheih” has long been a point of controversy among poskim. It is a question that requires a sound understanding of the principle of pesik reisheih. In the case of trapping an animal by closing the door to a room, would it be considered a pesik reisheih to close the door when there might not even be an animal inside? On the one hand, trapping an animal is not a certain consequence of closing the door, since there might not even be an animal inside. On the other hand, should an animal be inside, closing the door will certainly trap it.

Most cases of davar she’eino miskaven – the unintended result of an action – involve an uncertainty regarding the future. Will dragging the bench create a furrow? Will pouring wine on the altar extinguish the fire? Since the outcome is doubtful, such actions are permitted. In the case of a retroactive pesik reisheih, there is also an uncertainty, but it is a question of ignorance regarding the present, not the future. Is there an animal in the room now?

The following example might help illustrate this question further. If a person gently brushes against the door of a birdcage, it might, or might not, swing shut. In this case, the action cannot be labeled an action of “trapping” since the door might not close. However, if a person intentionally closes a door, even if he does not know whether there is an animal inside, his action is definitely an act of trapping since an animal that happens to be in that room would be trapped.

Thus, the controversy regarding davar she’eino miskaven focuses on cases in which it is unclear what consequences the action will bring about. Retroactive pesik reisheih can be considered when, due to our ignorance, the situation in the background of the action is uncertain. In such a case, poskim debate whether davar she’eino miskaven is applicable, and whether retroactive pesik reisheih is included in this lenient ruling.

Checking For Flies

The Taz (Orach Chayyim 316:3) rules that if one suspects that a box might contain flies, one may nevertheless close its lid without first checking to see if any flies are inside. One does not intend to trap any flies, and it is also uncertain whether there are flies in the box at all. Yet, the action of closing the box will certainly trap any flies that may be inside. This is a case in which the action is certain but the situation in the background of the action is uncertain. The Taz compares this case to a davar she’eino miskaven, which is permitted.

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RABBI YAAKOV KLASS, rav of Congregation K’hal Bnei Matisyahu in Flatbush, Brooklyn, is Torah Editor of The Jewish Press. He can be contacted at [email protected]. RABBI GERSHON TANNENBAUM, rav of Congregation Bnai Israel of Linden Heights, Boro Park, Brooklyn, is the Director of Igud HaRabbanim – The Rabbinical Alliance of America.