Keilim 18:7 - 18:8

כרע – [leg] of a bed which was impure with defilement by treading. That the person with gonorrhea tread on the bed leg when he was on its own and it was not connected to the med.

כולה טמאה מדרס – for attachment was done to it, as if it is all one body.

היתה טמאה טומאת שבעה – such as, for example, that it came in contact with a corpse.

טומאת ערב – that it came in contact with someone who was defiled through contact with a corpse.

והמטה טהורה – that it (8.e. the bed) was not defiled through contact of the leg [of the bed]. For it was first [degree of ritual impurity], and a person nor vessels are susceptible to defilement other than from a primary source of defilement.

מעדר (mattock, share of the plough/pitchfork for the first stage of winnowing – passing the grain from one side to the other) – a wooden vessel/utensil that has teeth that turn over the straw, and its teeth are metal. And because the teeth are of joints inserted therein, its law is like that of a bed which is of links. And this and similar to it, it is referring to the defilement for seven days, for the share of the plough does not defile through treading.

תפלה – it is speaking of the Tefillin of the head that came in contact with a corpse, for it has four compartments, and every compartment is called a קציצה/capsule, compartment.

התיר קציצה (he untied/loosened the compartment) – he removed one compartment and brought another in its place.

טמאה טמא מת – that their connection/attachment makes them one body.

וכן שניה וכן שלישית – all the time that the fourth [compartment] exists. On account that it is attached to the fourth [compartment]. But when he removed also the fourth and exchanged it for another, the defilement from [contact with] the dead flies out from it, and there remains in the three compartments/capsules [of the Tefillin of the head] the defilement from contact with something which had been defiled through contact with a corpse, for it came in contact with the fourth [capsule/compartment] when they attached them and it still exists. But the Fourth [capsule/compartment], when it was switched out, there is no defilement in its body at all, for if it was because it come in contact with the three [other] compartments, contact [uncleanness] does not cause contact uncleanness, since the first three [compartments] are new, that came in contact with someone who had been in contact with a corpse, the new forth [compartment] does not receive defilement from them, and there is no defilement in the new fourth [compartment] other than on account that is attached to the three which are defiled through contact. Therefore, when he return and switched out the three [compartments] a second time, all of them are pure, and there is no contact [with defilement] in them.