Leviticus 15:20

And everything on which she lies during her menstrual impurity shall be unclean . Everything also on which she sits shall be unclean .

“‘Anything she lies on during her period will be unclean, and anything she sits on will be unclean.

And every thing that she lieth upon in her separation shall be unclean : every thing also that she sitteth upon shall be unclean.