Kelim, Chapter Eighteen, Mishnah Five
Today’s mishnah deals with how much of a bed must be removed for it to be considered defective and therefore no longer unclean (or susceptible to impurity).
1) A bed that had contracted midras uncleanness:
a) If a short side was removed and its two legs still remains it is unclean.
b) But if a long side and two legs were removed it becomes clean.
c) Rabbi Nehemiah says: it is unclean.
2) If two props at opposite corners were cut off, or if two legs at opposite corners were cut off, or if the bed was reduced to a level of less than a handbreadth, it becomes clean.
Section one: Midras impurity is impurity conveyed when an object is sat upon or laid upon by a zav (one with abnormal genital discharge).
If the board on the short side of the bed, meaning the head or foot of the bed, was removed and with it its two legs the bed is still unclean, because it can still be used.
However, if one of the long sides is removed the bed can no longer be used because the person lying on it will fall off. Therefore the bed is clean.
Rabbi Nehemiah says that what remains is still unclean because he can use it by leaning it up against the wall or in some other way.
If we were to summarize the principle that emerges from this debate, the sages would say that a vessel that is broken and can no longer be used without support of another vessel is clean. Rabbi Nehemiah holds that as long as it can still be used, it is still unclean.
Section two: The “props” referred to here are the supports upon which the rectangle rests. If two props or two legs at opposite corners were cut off then the bed won’t be able to stand. In both cases the bed is clean because it is unusable. In addition, if he cuts down the legs so that the bed is lower than a handbreadth high, the bed is clean because it is considered unusable.