Ohalos, Chapter 7, Mishnah 3. Our mishnah continues the discussion of the doorway of a house in which a meis is lying. Chazal decreed tumah upon the opening through which the meis is destined to be carried out, so that keilim resting in that opening become tamei even before the meis has been moved. The question our mishnah takes up is what happens when the house has more than one possible exit, and how a decision (or an act) can narrow the tumah down to a single doorway.
Many openings, all of them locked
"HaMeis babayis, uftachim harbei": there is a meis lying in the house, and the house has a number of openings, whether doorways or windows, but every one of them is shut. Since there is nothing to indicate which one will be used, we have no way of knowing where the meis will eventually be taken out.
The mishnah rules "kulan temei'in": all of the openings are tamei. This includes any keli lying beneath the lintel, even a keli positioned on the outer side of the closed door. Picture a house with a small stoop: there is the doorframe, the door itself is locked, and a keli is sitting in the space of the doorway on the street side. Were you to reach down and lift that keli, your face would be up against the shut door. Nevertheless, that keli is tamei, because Chazal imposed tumah on the opening through which the meis is going to leave, and here every one of the openings is a candidate.
One opening is unlocked
"Niftach echad meihen, hu tamei vekulan tehorin": if one of these openings was opened, that one alone is tamei, and all the others are tahor from this point onward. Once a meis is in a house that has exactly one open exit, it is clear enough that this is the route by which he will be carried out. That opening and the keilim beneath it are tamei; the remaining openings, and keilim brought to them from now on, are tahor.
One may ask: what forces us to say that the meis will leave through the opening that happens to be unlocked? Perhaps the family will open a different door instead. The Mishnah Acharonah explains that people are eager to remove a meis from the house without delay. If a doorway already stands open, plain reasoning says that this is the way he will be taken out, and no one will trouble himself to unlock another entrance.
The Tosafos Yom Tov draws out a striking chiddush from this ruling: it holds even where no person opened that entrance and it came open of itself. One might have supposed that the other openings escape tumah precisely because someone chose to unlock this particular one and thereby disclosed his plan. That, however, is not the foundation of the halachah. Since the household is pressed to see to the burial without delay, and since one entrance in fact stands open, we presume the removal will take place there, however that entrance came to be open.
Deciding on an opening that is still closed
"Chashav lehotzi be'echad meihen, o bechalon shehu arba'ah al arba'ah tefachim, hitzil al kol hapesachim": the openings are all still shut, but the people in the house made up their minds to carry the meis out through a particular doorway, or through a particular window that measures four tefachim by four tefachim. That decision alone saves all the other openings, and keilim placed in them are tahor.
The four by four tefachim mentioned regarding the window is the shiur of an opening fit for removing a meis, and the same requirement applies to a doorway. An opening smaller than that is not a realistic exit, and settling on it accomplishes nothing.
When must the decision be made?
The Tannaim disagree about when this machshavah has to take place. Beis Shammai's position is "Yachshov ad shelo yamus hameis": the choice must be settled while the person is still living. Only a resolution arrived at before the petirah has the strength to restrict the tumah to a single opening. Should the neshamah have already departed and the family fix on a particular doorway only afterward, their decision comes too late and the remaining openings do not go free.
"Uveis Hillel omrim, af mishemeis": Beis Hillel hold that even after the person has died, a decision to use one particular opening removes the tumah from the rest.
The Bartenura points out that even according to Beis Hillel the relief operates only mikan ulehabah, from that moment forward. Keilim that were already lying in the other openings before the decision was made remain tamei, since at the time they were there each of those openings was still a possible exit. But keilim brought to those openings after the decision was made are tahor.
An opening sealed with stones
"Hayah sasum venimlach lepascho": one of the openings of the house had been sealed up with stones, and the family now decided to clear the stones away and carry the meis out through it.
"Beis Shammai omrim, kesheyiftach arba'ah tefachim": Beis Shammai hold that this opening will not save the others until four tefachim by four tefachim of stone have actually been removed. In their view, once an entrance has been blocked up with stones it is no longer an opening at all. Therefore even if the decision was made while the person was still alive, and even if the work of clearing the stones has begun, nothing is accomplished until an actual gap of four by four tefachim exists.
Beis Hillel again rule leniently: "Uveis Hillel omrim, kiyeschel." From the moment he starts taking the stones down, that entrance is established as the place from which the body will be brought out, and the remaining openings are rendered tahor. Observe, though, that Beis Hillel too demand more than machshavah in this instance. A door that merely needs unlocking can be designated by thought alone; a passage stopped up with stones requires that the dismantling actually be underway. All that Beis Hillel ease here is the measure: a full four by four tefachim need not yet be cleared, so long as the work of removing the stones has been begun.
Cutting a brand new opening
"Umodim biposei'ach bat'chilah, sheyiftach arba'ah tefachim": Beis Hillel agree with Beis Shammai in a case where there was never an opening in that spot at all. Suppose the family decides that they wish to bring the meis out through a certain wall, and since one cannot pass through a wall they will cut a new doorway into it. In such a case the other openings are not saved until an area of four tefachim by four tefachim has actually been opened up, and this is the halachah even according to Beis Hillel.
Reviewing the mishnah
A meis is lying in a house that has numerous openings, none of them open. Every one of them carries tumah, and that includes a keli sitting within the doorframe on the street side of the locked door, for Chazal imposed tumah upon the opening designated for removing the meis, and any one of these might turn out to be that opening.
If one opening was opened, that opening is tamei and the rest are tahor from that moment onward: keilim brought to them afterward are tahor, while keilim that had been lying there until then remain tamei, as the Bartenura teaches. The same is true if the family merely decided to use one particular doorway or one particular window of four by four tefachim, even though it is still closed: that determination saves the other openings.
As for when that determination must be made, Beis Shammai require it before the person's petirah, while Beis Hillel hold that even after the neshamah has departed and the meis is lying in the house, a decision to use one opening renders the others tahor, again only from that point onward.
If an opening had been sealed with stones and the family resolved to clear them away and carry the meis out there, Beis Shammai treat it as though there were no opening at all, so that it saves the others only once four by four tefachim of stone have been removed, that being the shiur of an opening fit for carrying out a meis. Beis Hillel concede that mere machshavah is insufficient here, since in practice the entrance is blocked with stones, but they hold that it is enough to begin the work of removal. And Beis Hillel agree that where there is no opening whatsoever and the family intends to break through a wall and fashion a new doorway, the other openings are not saved until at least four by four tefachim of that new opening have been made.