Leviticus 15:19-23

19“Whenever a woman has her menstrual period, she will be ceremonially unclean for seven days. Anyone who touches her during that time will be unclean until evening.

20Anything on which the woman lies or sits during the time of her period will be unclean.

21If any of you touch her bed, you must wash your clothes and bathe yourself in water, and you will remain unclean until evening.

22If you touch any object she has sat on, you must wash your clothes and bathe yourself in water, and you will remain unclean until evening.

23This includes her bed or any other object she has sat on; you will be unclean until evening if you touch it.