John Gill Commentary Leviticus 13:44

"he is a leprous man, he is unclean: the priest shall surely pronounce him unclean; his plague is in his head." — Leviticus 13:44 (ASV)

He is a leprous man, he [is] unclean
And so to be pronounced and accounted; only a leprous man is mentioned, there being no leprous women, having this sort of leprosy, their hair not falling off, or they becoming bald, usually; unless, as Ben Gersom observes, in a manner strange and wonderful:

the priest shall pronounce him utterly unclean ;
as in any other case of leprosy:

his plague [is] in his head ;
an emblem of such who have imbibed bad notions and erroneous principles, and are therefore, like the leper, to be avoided and rejected from the communion of the saints, (Titus 3:10) ; and shows that men are accountable for their principles as well as practices, and liable to be punished for them.