Trespass offering: To be offered for Involuntarily Touching Unclean Things

Or if a person touches anything unclean—whether the carcass of any unclean wild animal or livestock or crawling creature—even if he is unaware of it, he is unclean and guilty.

Or if he touches human uncleanness—anything by which one becomes unclean—even if he is unaware of it, when he realizes it, he is guilty.