Negaim 3:5

A nega of the hair or beard becomes unclean for two weeks based two signs: thin yellow hair or spreading. Thin yellow hair is at the outset, at the end of the first week, at the end of the second week or after being released; spreading is at the end of the first week, at the end of the second week or after being released. It is rendered unclean for two weeks that are 13 days.

Negaim 3:6

Baldness of the scalp or forehead becomes unclean for two weeks based on two signs: by healthy flesh or by spreading. Healthy flesh is at the outset, at the end of the first week, at the end of the second week or after being released; spreading is at the end of the first week, at the end of the second week or after being released. It is rendered unclean for two weeks that are 13 days.