משנה אויף ויקרא 15:13

There are ten [grades of] impurity that emanate from a person:A person before the offering of his obligatory sacrifices is forbidden to eat holy things but permitted to eat terumah and [second] tithe. If he is a tevul yom he is forbidden to eat holy things and terumah but permitted to eat [second] tithe. If he emitted semen he is forbidden to eat any of the three. If he had intercourse with a menstruant he defiles the bottom [bedding] upon which he lies as he does the top [bedding]. If he is a zav who has seen two discharges he conveys impurity to that on which he lies or sits and is required to undergo immersion in running water, but he is exempt from the sacrifice. If he saw three discharges he must bring the sacrifice. If he is a metzora that was only enclosed he conveys impurity by entry [into an ohel] but is exempt from loosening his hair, from rending his clothes, from shaving and from the birds offering. But if he was a confirmed metzora, he is liable for all these. If a limb on which there was not the proper quantity of flesh was severed from a person, it conveys impurity by contact and by carriage but not by ohel. But if it has the proper quantity of flesh it conveys impurity by contact, by carriage and by ohel. A "proper quantity of flesh" is such as is capable of healing. Rabbi Judah says: if in one place it has flesh sufficient to surround it with [the thickness of] a thread of the woof it is capable of healing.

Superior to them are "smitten waters" which can purify even when flowing [on the ground]. Superior to them are "living waters" for in them there is immersion for zavim and sprinkling for metzoraim, and they are valid for the preparation of the hatat waters.

He may donate his terumah and his tithes with his consent. He may offer up for him the bird sacrifices of zavim and zavoth and the bird sacrifices of women after childbirth, sin-offerings and guilt-offerings. He may teach him midrash, halakhoth and aggadoth, but not Scripture, yet he may teach his sons and daughters Scripture And he may support his wife and children, even though he is liable for their maintenance. But he may not feed his beasts, whether clean or unclean. Rabbi Eliezer says: he may feed an unclean beast of his, but not a clean one. They said to him: what is the difference between an unclean and a clean beast? He replied to them, a clean beast, its life belongs to heaven, but its body is his own; but an unclean animal its body and life belongs to heaven. They said to him: The life of an unclean beast too belongs to heaven and the body is his own for if he wishes, he can sell it to a non-Jew or feed dogs with it.