8And the priest shall look, and if the eruption has spread in the skin, then the priest shall pronounce him unclean; it is a leprous disease.
If the infection spread after the first evaluation, a second test was required. If the infection had clearly spread, then the priest would declare the Israelite to be unclean. Such a state would indicate the presence of a malignant skin disease.
8 And the priest shall look, and if the eruption has spread in the skin, then the priest shall pronounce him unclean; it is a leprous disease.