1) THE PURIFICATION PROCESS OF A "ZAV"
QUESTION: The Beraisa derives from the verse, "When the Zav becomes Tahor" (Vayikra 15:13), that "he counts seven days when he stops seeing the flow." The Beraisa derives from the continuation of the verse, "[When the Zav becomes Tahor] from his discharge (mi'Zovo)," that a Zav who is also a Metzora starts counting when his discharge has stopped and he does not have to wait until he is Tahor from the other type of Tum'ah ("mi'Zovo v'Lo mi'Neg'o") in order to start counting the days of Taharah for his Tum'ah of Zav.
What is the point of the Beraisa's first Derashah? The Beraisa says that when the Zav stops seeing a discharge, he may start counting the seven days. This, however, is obvious. What would one have assumed without the verse?
(a) RASHI explains that one would have thought that a Zav must immerse in a Mikvah immediately after his discharge stops, before he starts to count. The verse teaches that he does not have to immerse after the discharge stops before he starts his count, but he may count his days of Taharah first.
The SHITAH MEKUBETZES in Megilah (the commentary of a Rishon printed by Rav Avraham Shoshanah, Ofek Institute, 5759/1999) questions Rashi's explanation. Rashi's words imply that if a Zav wants to immerse before he starts to count, he may immerse at the moment his discharge stops and he does not have to immerse after he finishes counting his days of Taharah. This implication clearly contradicts the law; one certainly must immerse after he counts seven clean days.
(b) Perhaps Rashi means to say something else. Without the verse, one would have thought that a Zav must immerse twice -- once before he starts to count and once after he counts. The verse teaches that he needs to immerse only once, after he counts.
This approach, however, is also problematic. On what grounds would one have thought that a Zav must immerse twice?
(c) The RITVA implies that the two Derashos of the Beraisa are not two separate Derashos, but are one Derashah. The Beraisa means that a Zav may count the seven days as soon as his discharge stops, and he does not need to wait for the cessation of any other Tum'ah which he might have (such as the Tum'ah of Tzara'as).
This may also be the intention of Rashi. When Rashi says that the Zav does not need to immerse before he starts to count, he means that the Zav does not need to immerse for his Tum'as Tzara'as, but rather he may start to count (the days of Taharah for his Tum'ah of Zav) immediately when his flow stops, even though he is still Tamei with Tum'as Tzara'as. (The words of Rashi are less accurate according to this explanation. Rashi says, "... rather, from the time his flow stops he may count." According to this explanation, however, the Zav is permitted to wait until his Tum'ah of Tzara'as passes before he starts to count, if he so chooses.)
2) HOW TO BECOME A "METZORA MUCHLAT"
QUESTION: RASHI in the Mishnah defines a "Metzora Muchlat" as the status of a Metzora "after the seven days of Hesger (isolation) have passed and the Nega shows signs of Tum'ah." At that point the Metzora becomes a Metzora Muchlat.
Why does Rashi mention that a Metzora becomes Muchlat after the days of Hesger have passed? The Mishnah in Nega'im (3:3) derives from the verses (see Vayikra 13:3) that if signs of Tum'ah appear (such as two white hairs or a healthy spot in the center of a Nega), the person immediately becomes a Metzora Muchlat without first having to undergo the stage of a Metzora Musgar. (Only with regard to the Siman Tum'ah of spreading, "Pisyon," does a Metzora become a Metzora Muchlat only after he was first a Metzora Musgar.) Why does Rashi describe a Metzora Muchlat as one who has already been isolated for a week and then signs of Tum'ah appeared? Becoming a Metzora Muchlat does not depend on being isolated (Musgar) for a week! (RASHASH)
ANSWER: The PORAS YOSEF answers that Rashi apparently follows his own opinion in his commentary on the Chumash. Rashi (to Vayikra 13:6) writes that the verse implies that if a Nega remains unchanged on a person's skin for two weeks' worth of isolation, the person becomes Tamei even though the Nega has not grown. The person becomes Tahor after two weeks of Hesger only when the Nega remains the same size (it does not grow) and it becomes lighter in color.
Based on that understanding, Rashi here may mean that there are two ways for a Metzora to become a Metzora Muchlat. First, he becomes a Metzora Muchlat if the days of Hesger pass and nothing changes (since Rashi maintains that a Nega which does not change after Hesger is Tamei). Second, he becomes a Metzora Muchlat right away if the signs of Tum'ah appear at any point, even before Hesger. (The "Vav" in Rashi here means "or.")
The RAMBAN challenges Rashi from the Gemara here. The Gemara clearly says that the Taharah of a Metzora Musgar depends on "days" and not on his physical condition ("b'Gufo"). As long as the days of his isolation have passed without any change in the Nega, he is Tahor. Hence, a Metzora Musgar becomes Tahor even when nothing on his body changes.
Perhaps Rashi maintains that when the Gemara says that the Taharah of a Metzora Musgar depends on days and not on his physical state, it means that the Metzora does not need to wait until the Nega is physically healed. Rather, he becomes Tahor when the Nega's whitish color becomes slightly whiter, even though the Nega is not actually healed and is still white enough to be considered a Nega of Tzara'as under other circumstances (i.e. had this been the first time it was examined). His Taharah depends on the days of his isolation passing and his Nega becoming slightly whiter, but it does not depend upon being healed (like the Taharah of a Metzora Muchlat, which depends on the Nega becoming "healed" by the disappearance of the signs of Tum'ah). This is similar to the Gemara's next description of the Metzora Musgar; the Gemara says that his Taharah does not depend on "Refu'os," which means that he does not need to wait for a physical healing process to take place.
This might explain why Rashi (DH Asher Bo) writes that when the Gemara says that the Metzora Muchlat's Taharah is "Taluy b'Gufo" it means that he must wait "until it is healed." Rashi means that his Taharah depends on the Nega having healed so that it is no longer a Nega. In contrast, a Metzora Musgar's Taharah depends on the Nega having changed (become lighter), even though it has not healed.