Kelim, Chapter One, Mishnah Three
We continue moving up the line of defiling agents.
1) Above them is one who had intercourse with a menstruant, for he defiles the bottom [bedding] upon which he lies as he does the top [bedding].
2) Above them is the issue of a zav, his spit, his semen and his urine, and the blood of a menstruant, for they convey impurity both by contact and by carrying.
3) Above them is an object on which one can ride, for it conveys impurity even when it lies under a heavy stone.
4) Above the object on which one can ride is that on which one can lie, for contact is the same as its carrying.
5) Above the object on which one can lie is the zav, for a zav conveys impurity to the object on which he lies, while the object on which he lies cannot convey the same impurity to that upon which it lies.
Section one: The impurity of a man who has sex with a menstruant is referred to in Leviticus 15:24: “And if a man lies with her, her impurity is communicated to him; he shall be unclean seven days, and any bedding on which he lies shall become unclean.” The rabbis interpret the end of this verse to mean that no matter how much bedding lies beneath him, they are all impure. The bedding will have first degree impurity, which means it defiles food and drink, but not other people or vessels.
Section two: Fluids which come out of the zav (spit, semen and urine) and menstrual blood convey impurity to a person by carrying and contact, such that he in turn conveys impurity to his clothing. This is different from the impurities mentioned above in mishnah two, which through contact do not defile a person such that he defiles his clothing. And a person who has sex with a menstruant does not defile others by being carried.
Section three: If a zav sits on a heavy stone, and underneath the stone there is a vessel used for riding (such as a saddle) the vessel is impure even though the stone cannot become impure. This is a special characteristic of something that is ridden upon.
Section four: Something that a zav lies upon (and is a vessel used for lying down, such as a bed) is even more serious in its impurity than something upon which he rides, in that the former conveys impurity through both contact and carrying. Furthermore, if someone has contact with something upon which the zav lay, he will himself further convey impurity to clothing. In contrast, one who has contact with something upon which the zav rides, does not defile clothing.
Section five: The zav himself can cause anything upon which he lies to become a defiling agent. However, the thing upon which he lies does not itself cause other bedding to become a “father of impurity.” Rather, anything it touches just has “first degree impurity.” We will learn more about the implications of being either a “father of impurity” or merely a “first” or lower degree of impurity as we proceed.