A baheres half the size of a gris has no [other symptoms] inside it. [Another] baheres half the size of a gris appears that has two hairs. This nega is confirmed, because [the Sages] stated: If the baheres preceded the white hair, [the afflicted person] is tamei, but if the white hair preceded the baheres, he is tahor. If it is uncertain, [the afflicted person] is tamei, but R’ Yehoshua disapproves [of this ruling].

Any doubt concerning negaim is ruled tahor, except for this [last] case and [the next] one. And what is [the next case]? Someone had a baheres the size of a gris that [the Kohen] confined. At the end of the week [of confinement], it was the size of a sela, [but] it is uncertain whether this is [the original nega that spread] or a different [nega] that replaced it. [The Kohen rules it confirmed] tamei.