Leviticus 15:20
And every thing that she lieth upon in her separation shall be unclean: every thing also that she sitteth upon shall 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.
Everything a woman lies upon in her separation becomes unclean, and everything she sits upon becomes unclean. This stands as part of the laws concerning bodily discharges and ritual uncleanness, covering the bed and anything used as a seat during the menstrual period. The rule served to contain infectious disease by preventing it from being communicated to others through shared contact with the bed or seat made unclean during that time. It belongs to the laws of physical uncleanness and cleansing in which a defiled object had to be visibly cleansed before the sanctuary could undergo its cleansing with blood. That order illustrates the distinction between removing physical uncleanness from objects and the sanctuary's later cleansing from moral defilement.
The minuteness of such regulations is a divine object-lesson emphasizing the exceeding sinfulness of sin everywhere. That detail takes on new life and blessing when seen as a type of Jesus Christ as the Lamb of God who takes away the sin of the world. The cleansing laws given to ancient Israel are an example of cleansing that God's people must not abandon. They apply to obedience to health principles and to health reform, which cleanse the body as a dwelling place for God's Spirit and prepare people to receive the latter rain.