מסכת כלים

פרק כז משנה יא

שלשה על שלשה

that tore (but did not split completely in two),

if placed on a chair (and one sat on it)

and the flesh (of a person sitting on the chair) touches the chair

it is tahor (from midras),

and if not it is tamei.

that one thread from it wore out (but remained attached),

or a knot was found in it

or two threads

alongside each other (that is to say, either two knots were found adjacent to each other where torn threads had been repaired, or two threads were woven in the identical over-under pattern, rather than one being over-under and the other under-over, which would happen if when being woven, the heddles of the loom were not alternately raised and lowered in between two passes of the shuttle bearing the weft yarn),

is tahor. (In the cases of the worn out thread, it is too insignificant to count as part of the material; the same would go for the second of the two parallel threads.  In the case of the two knots, because of the protrusion they cause, one would be bound to untie of of the knots and replace the entire torn thread, and so it too does not count).

that was thrown into the trash heaps

is tahor;

if it is retrieved it is (able to become) tamei;

Always, throwing it out makes it tahor

and retrieval makes it (able to become) tamei,

except for purple cloth

and of good crimson (which are valuable, and so retain their status even when thrown out);

Rabbi Eliezer says,

also a patch of new material

is like them;

Rabbi Shimon says

all of them are tahor,

they did not mention (this differentiation of purple and fine crimson material)

except for returning lost items. (If one finds such an item in a trash heap, one must assume it got there accidentally and that the owner will hope to recover it.  As such, attempts must be made to return it.)

שלש על שלש

that was put inside a ball (as stuffing),

or was itself made into a ball,

is tahor (as this demonstrated an intent to no longer use it as a cloth).

But three by three (handbreadths of cloth)

that was put inside a ball

is tamei

if it itself was made into a ball (and it measured precisely three by three handbreadths)

it is tahor

as the stitching reduced its size.