Leviticus 13:5-8

13:5 The priest must then examine it on the seventh day, and if, as far as he can see, the infection has stayed the same and has not spread on the skin, then the priest is to quarantine the person for another seven days. 13:6 The priest must then examine it again on the seventh day, and if the infection has faded and has not spread on the skin, then the priest is to pronounce the person clean. It is a scab, so he must wash his clothes and be clean. 13:7 If, however, the scab is spreading further on the skin after he has shown himself to the priest for his purification, then he must show himself to the priest a second time. 13:8 The priest must then examine it, and if the scab has spread on the skin, then the priest is to pronounce the person unclean. It is a disease.