משנה על מכשירין 4:13

Above the zav is the zavah, for she conveys impurity to the man who has intercourse with her. Above the zavah is the metzora, for he conveys impurity by entering into a house. Above the metzora is a [human] bone the size of a barley grain, for it conveys impurity for seven days. More strict than all these is a corpse, for it conveys impurity by ohel (tent) whereby all the others convey no impurity.

Above the zav is the zavah, for she conveys impurity to the man who has intercourse with her. Above the zavah is the metzora, for he conveys impurity by entering into a house. Above the metzora is a [human] bone the size of a barley grain, for it conveys impurity for seven days. More strict than all these is a corpse, for it conveys impurity by ohel (tent) whereby all the others convey no impurity.