Keilim, Chapter 18, Mishnah 6. This mishnah continues the chapter's discussion of a bed and its parts, and it asks what happens to a bed that already carries tum'at midras when its long sideboards break and are replaced one after the other. The question is not only whether the bed still functions, but whether the bed standing before us is still the same bed that once received the tum'ah.
The Mishnah opens: "Mitah shehaytah teme'ah midras", a bed that had become tamei with tum'at midras, meaning it had been lain upon by a zav or a similar person whose lying transmits midras tum'ah, making the bed an av hatum'ah. The following halachot apply to it.
The first sideboard breaks
"Nishberah arukah vetiknah, teme'ah midras": one of the two long boards along the side of the bed snapped, and a fresh board was fitted into the empty place so that the bed could be used again. Its status has not moved at all: the bed carries tum'at midras just as it did before the break. A single board giving way is not enough to change anything, since the rest of the bed remained intact throughout. The very keli that once absorbed the tum'ah is still here in front of us, and swapping in one component does not create a different object.
The second sideboard breaks
"Nishberah sheniyah vetiknah, tehorah min hamidras": afterwards the second long sideboard broke as well, and the owner again repaired the bed with a new sideboard. Now the bed is tahor from tum'at midras and is no longer an av hatum'ah.
This ruling sounds strange at first, because there was never a moment when the bed ceased to be usable as a bed. Yet with the replacement of the second board the tum'at midras has vanished completely. The principle behind it is this: we examine whatever survives from the original bed and ask whether that leftover material, by itself, would still be a serviceable bed, and the answer is no. The two long boards holding the bed up are both new, and neither of them was ever subject to tum'at midras. Because the remnants of the old bed could not stand as a keli at all without these two fresh boards, halachah views the item before us as a bed newly born. From this point on it bears no midras tum'ah.
But it is still tamei by contact
"Aval teme'ah maga midras": the bed is still tamei, though on a lower level, as a keli that came into contact with something bearing tum'at midras, which makes it a rishon letum'ah. Follow the chain carefully.
- To begin with, the bed had the status of an av hatum'ah by way of midras.
- After the first break, when a new board was inserted, the bed's midras tum'ah was still fully in force, since only one of the two boards had changed. That new board thus made contact with an av hatum'ah and became a rishon letum'ah.
- With the breaking of the second board, the midras tum'ah departed, for the reason explained: this is no longer the keli that had been lain upon. The board installed earlier, however, retains its status as a rishon.
- Everything else in the bed is joined to that rishon board and draws tum'ah from it, so that the reconstituted bed is itself a rishon.
In other words, there is a transfer taking place here. The tum'ah moves from the original bed to the first new board, and then from that board to the reconstructed bed, so that what remains is not midras but contact tum'ah at the level of a rishon.
When both boards broke before either was repaired
"Lo hispik letaken et harishonah ad shenishberah hasheniyah, tehorah": if the first break had not yet been mended by the time the second board gave way, the bed emerges entirely tahor. Once that second board snapped, there was nothing left that could serve as a bed, and at that instant all of its tum'ah departed.
The practical difference between the cases lies precisely in that timing. Here, when the new boards were finally installed, there was no longer any tamei keli for them to touch, so the new boards never became tamei at all. Both sideboards were broken, the bed was no longer a keli, the tum'ah was gone, and only then were both boards replaced together. Since nothing tamei was present to transfer tum'ah to the new boards, there is no rishon in the picture, unlike the earlier case where the first replacement board did become a rishon. What results is treated as a completely new bed, tahor in every respect.