Halakhah su Levitico 13:59

And the author of the Halakhot Gedolot was already aware of some of these matters and went around them by counting sections (as a whole and not each part of them). And in counting them, he [called them], the section of inheritances, the section of vows and oaths, the section of putting out a bad name. And he counted many sections like this. However he was not completely clear about this topic and did not arrive at it [fully]. And hence he counted in these sections that which had already been counted earlier, without sensing it. And since this principle escaped those besides us concerning the commandment of tsaraat, he counted it as twelve commandments and did not know that they are [actually just] one commandment; and that everything mentioned by Scripture is actually a detail or a condition. And the explanation of this is that He instructed us that tsaraat of a person makes one impure; and his impurity is such that he is obligated regarding that which impure people are obligated regarding distancing from the Sanctuary and its holy things, and to go outside of the camp of the Divine Presence. But we would not [yet] know which tsaraat renders impure and which does not render impure. So Scripture came to explain it and differentiate the regulations, such that if he was like this, he would be pure, but if he was like that he would be impure; if he was like this, he would have to stand so much time like this, but if he was like that, he would have to stand [a different amount of] time. And in explanation, they said (Sifra, Tazria Parashat Nega'im, Chapter 16:13), "'To declare it pure or to declare it impure' (Leviticus 13:59) - just as it is a commandment to declare it pure, so it is a commandment to declare it impure." So the commandment is in fact for [a priest] to say, impure or pure. However it is inappropriate to count the differentiations of the their content - such that some are impure and some are pure - since they are its conditions and details. And this is like our saying that sacrificing animals with defects is forbidden to us. But if [we understand that] it is a negative commandment, it remains for us to know what the defects are. Could you see us calculating each and every defect as a commandment? If this were the case, its count would be close to seventy defects. But just like we do not count the defects - which of them are [an actual] defect and which of them are not [an actual] defect - but rather the prohibition is that we have been prohibited from an animal with a defect; so too is not fitting to count all of the signs of tsaraat - which of them are impure and which of them are pure - but rather only that the person with tsaraat is impure. And all of the rest is an explanation of what tsaraat is. And in this way, it it appropriate to count each and every type of impurity as one commandment [each]; and not count all the details of that type of impurity and its conditions, as will be explained. And understand this principle, as it is a pillar of the teaching in which we are [involved].

And afterwards, the priest shaves the metsora. And how does he shave him? He passes the razor over his visible flesh - and even [on] the underarm and the pubic area and all the rest of the body - until he becomes [smooth] like a gourd, as it is stated (Leviticus 14:9), "all of his hair." If so, why does it state, "his head, his beard, and his eyebrows?" To include everything that is like them and to exclude hair that is in the nose, since it is not seen. And afterwards he washes his clothes and immerses, and is purified with this from passing on impurity from his resting and sitting [upon something]; and he can come inside the [city] wall. And he counts seven days; and during those seven days, he is prohibited in sexual relations, as it is stated, "outside of his tent" - teaching he is forbidden in sexual relations. But a metsora'at is permitted in sexual relations. All of these seven days, he is still a source of impurity and renders a person and vessels impure with touch, but he does render impure with carrying - as behold it states (Leviticus 14:9), "And it shall be on the seventh day, etc. and he shall wash his clothes" - teaching that he was rendering clothes impure. And [just] like he was rendering clothes impure, so [too] was he rendering a man impure with touch - since all that renders a person impure, renders clothes impure; and all that does not render a person impure, does not render clothes impure (Mishnah Kelim 1:1). And on the seventh day, the priest shaves him a second [time] like the first shaving. And [the metsora] washes his clothes and immerses and is purified from rendering others impure. And behold he is like all who have immersed during the day, and can eat from the tithe; when his sun sets, he can eat from the priestly tithe; [and] when he brings his atonement, he can eat from consecrated foods. The slaughter of the bird, the shaving and the sprinkling are during the day, but all the other procedures are whether during the day or during the night. These [three things] are with men, but all the rest are even with women. These are with priests, but all the rest are even through an Israelite. And it is a commandment for the same priest who rendered him impure [to render him pure, as it is stated (Leviticus 13:59)], "to render him pure or to render him impure." And the rest of its details are in Tractate Negaim.