John Gill Commentary Leviticus 15:22

"And whosoever toucheth anything that she sitteth upon shall wash his clothes, and bathe himself in water, and be unclean until the even." — Leviticus 15:22 (ASV)

And whosoever touches anything that she sat upon
Which was appropriated to her to sit upon, as the Targum of Jonathan, which was her proper and peculiar seat, what she usually sat upon; such were obliged to wash their clothes and bathe, as in all the above cases. See (Leviticus 15:5Leviticus 15:10) .