Why is the 'Gimel' in "Vehisgalach" big?
What does the Pasuk mean when it writes "ve'es ha'Nesek Lo Yegale'ach"?
Rashi and Ramban #2 citing Toras Kohanim: It means that the Kohen must leave two hairs at the extremity of the Nesek, so that it will be discernable should it spread during the seven days quarantine.
Ramban #1: It is a Lo Sa'aseh against shaving the skin of the Nesek. 1
Because it prevents hair from growing there (Ramban).