Rashi on Leviticus 13:57/רש"י על ויקרא י״ג:נ״ז

1פרחת היא IT IS A SPREADING PLAGUE — it is a thing which breaks out again and again.

2באש תשרפנו THOU SHALT BURN IT IN FIRE — “it” — the entire garment (in contradistinction to v. 56).