Comentário sobre Kelim 27:9

ועשאו וילון – a curtain that is front of the opening, as for example, that he made something that by means of it is pure from uncleanness through treading, according to the School of Shammai from when it is sewn, but according to the School of Hillel, from when it is tied up. But according to Rabbi Akiba, from when one fixed it, as is taught in the Mishnah above in [Tractate Kelim] the Chapter, “The Mattresses and the Pillows”/"הכרים והכסתות" (Chapter 20) [Mishnah 6[.

If a sheet that had contracted midras uncleanness was made into a curtain, it is pure from midras uncleanness but is still unclean from contact with midras uncleanness. Once he turns the sheet into a curtain it loses its midras impurity because it is no longer something that is sat or lain upon. However, the curtain is considered to have had "contact with itself," and therefore it is still unclean by virtue of contact with midras uncleanness.

טהור מן המדרס – that it is annulled from the law of lying and sitting, but it is appropriate to the defilement of contact, because the attendant warms himself in it and wraps himself in his rims.

Rabbi Yose said: but what midras uncleanness has this touched! Only if a zav had touched it is it unclean from contact with a zav. Rabbi Yose holds that having "contact with itself" does not cause something to be impure. In other words, if the sheet/curtain is no longer impure with midras, then it is not impure by virtue of contact with midras. However, this does not necessarily mean that the curtain (former sheet) is pure. If a zav (the one who conveys midras impurity) touched it when it was a sheet, he gave it both midras impurity because he sat on it and contact impurity by touching it. When it becomes a curtain, it loses its midras impurity because it is no longer sat or lain upon, but it retains its impurity by virtue of contact with the zav. Note that if the zav had sat or lain upon the sheet without touching it, it would have only had midras impurity and when it was turned into a sheet it would be completely pure.

וכי באיזה מדרס נגע זה – meaning to say, since it is ritually pure from the defilement of treading when he made it into a curtain, it is completely pure and there doesn’t remain in it any defilement. For anything that were shards of vessels are pure from their defilement completely.

אלא אם כן נגע בו הזב – if the person with gonorrhea/flux came in contact with this curtain, he defiles it with the defilement of the contact of a person with gonorrhea. But from the power of defilement of treading that was in it initially, there is no defilement here at all. But the Halakha is not according to Rabbi Yossi.