Charles Ellicott Commentary Leviticus 15:4

"Every bed whereon he that hath the issue lieth shall be unclean; and everything whereon he sitteth shall be unclean." — Leviticus 15:4 (ASV)

Every bed, whereon he lieth. —So severely did the canonical law deal with these cases that they interpreted the defilement communicated to the bed, and hence also to his seat and saddle, by the patient in five different ways: by standing, sitting, lying, hanging, or leaning on it. The patient’s polluting power is so great that even if the bed, seat, or saddle is under a stone, he defiles it through the stone by any of these actions. If he stood upon two beds, placing one foot upon each, he defiled both.