Why does the Pasuk use the expression "Zos ha'Torah"?
Seforno: To teach us that whoever comes to Pasken the laws of Nega'im, must be able to distinguish between two kinds of Nega'im, even if they belong to the same category - such as the difference between Nega Tzara'as and Nesakim (both on a person's skin), 1 as the Torah goes on to explain. 2
The latter are Tamei by the hair falling out, whereas the former require one of the four appearances (Refer to 13:30:1:1*).
And by the same token, he must be able to distinguish between Tzara'as on a garment and Tzara'as on a room, even though both are supernatural and both occur by means of a deep red or deep yellow mark on the skin - if the Nega spreads after the first week, the former is obligated to replace the stones and the mortar ... , whereas the latter is Tamei and must be burnt. And by the same token again, he must be able to distinguish between a Se'es, a Sapachas and a Baheres, even though they all occur by a white mark on the skin and are examined for the same signs and they even combine, the examiner must be able to distinguish between the different shades of white and their locations (as the Torah explains in Pasuk 55 and 560, bearing in mind that a Nega on the location of a boil and a burn can combine, whereas a scar on the same location and on the location of hair is not examined for an appearance at all (Seforno).
Seeing as (in Pasuk 56) the Pasuk mentions Se'eis Sapachas and Baheres , what is "le'Chol 'Nega Tzara'as" referring to?