מסכת כלים

פרק יט משנה ד

If a zav is supported by a bed

and on a mizran (a strap of cloth wrapped around the outside of the bed to help keep the boards and legs together; the mishnah refers here to when the zav sat on the bed while the mizran was wrapped around it),

it imparts tumah to two and disqualifies one (this means that the bed and mizran become an av hatumah; this means that a chain of two items can become tamei from them, the first item that contacts them directly becomes a rishon, and that item can then impart tumah to food which becomes a sheini, then if that sheini touches terumah disqualifies it and renders it forbidden to consume),

this is the opinion of Rabbi Meir.

Rabbi Yosi says

and on a mizran of ten handbreadths (these ten handbreadths extend from the part of it wrapped already around the bed)

it (the bed and mizran) imparts tumah to two and disqualifies one;

from ten [handbreadths] and outward [of the mizran]

it [the mizran] imparts tumah to one and disqualifies one (i.e. it is a rishon, and not an av),

if he was supported by the mizran (the excess portion of the mizran that is not wrapped around the bed)

from ten [handbreadths] and inwards (the bed and mizran) is tamei,

from ten [handbreadths] and outwards is tahor.

A bed

and one wrapped a mizran around it,

the entire [assembly of bed and mizran] are tamei midras,

if it was removed,

it [the bed] is tamei midras

and the mizran is tamei from contact with midras;

if it was tamei with seven-day tumah (this is tumah an object incurs from a cadaver)

and one wrapped a mizran around it,

if it was removed,

it [the bed] is tamei with seven-day tumah

and the mizran is tamei the tumah of a night (i.e. it may be immersed immediately and becomes tahor that night);

if it was tamei the tumah of a night,

and one wrapped a mizran around it,

if it was removed,

it [the bed] is tamei the tumah of a night

and the mizran is tahor.