Halakhah sur Le Lévitique 13:33

To not shave the hair of the scab: To not shave the hair of the scab (netek), as it is stated (Leviticus 13:33), "but the scab, he shall not shave" - meaning to say that hair that is on the place of the scab, he shall not shave. And the language of Sifra, Tazria, Parashat Nega'im, Chapter 9:7 is "From where [do I know] that one who detaches the signs of impurity from within his scab, that he violates a negative commandment? As it is stated, 'but the scab, he shall not shave.'" And the matter is that the priest recognize the signs of impurity in the hairs.