Keilim 1:4-5
Keilim 1:4
Even higher than a zav is a zavah (a woman who has had a particular type of genital discharge), since she can convey ritual impurity to a man through sexual intimacy. Higher than a zavah is a metzora (colloquially, a “leper” but not really), who conveys ritual impurity by entering a structure (a building or a tent). Higher than a metzora is a piece of human bone the size of a barleycorn, which conveys ritual impurity that lasts for seven days. The most stringent transmitter of ritual impurity is a corpse which, unlike all the others, conveys ritual impurity just by being under the same canopy.
Keilim 1:5
A man can experience ten different levels of ritual impurity. One who needs to bring his atonement offering may not eat from sacrifices but he can eat trumah and tithes. If he immersed and is waiting for nightfall, may not eat from sacrifices and trumah but he can eat tithes. If he experienced a seminal emission, he may not eat any of these things. If he was sexually intimate with a niddah (a menstruant woman), he conveys impurity to the bottom mattress just as he does the top mattress. If he is a zav who saw two genital discharges, he conveys ritual impurity to things upon which he might lie or sit and he must immerse in running water but he need not bring an offering; if he saw three discharges, he must bring the necessary offering. If he is a quarantined metzora, he conveys ritual impurity by entering a structure but he need not let his hair grow wild, rend his clothes, shave or bring an offering of birds; if he is confirmed as a metzora, he must do all these things. If a limb on which there was not a sufficient volume of flesh was severed from a person, it conveys ritual impurity by contact and carrying but not by being under the same canopy; if it has the sufficient volume of flesh, it conveys ritual impurity by contact, carrying and by being under the same canopy. This volume of flesh is enough that it could heal. Rabbi Yehuda says if there’s enough flesh in one place to surround the limb with strips as thick as a woof thread (i.e., thick thread), it is considered enough that it could heal.