unclean: "Clean" and "unclean" did not relate to hygiene (see Leviticus 11:1–15:33). They referred to whether someone could participate in worship. For animals, it meant if they were suitable for sacrifice or eating. There is a list of ceremonially clean and unclean animals in 11:1–47.
To become ceremonially clean after touching an unclean animal, a person had to wash their clothes. They also had to stay away from the community until evening (11:25). This sin offering probably shows that the person did not follow the rules for cleansing (11:27–28).