Leviticus 15:20-21

15:20 Anything she lies on during her menstruation will be unclean, and anything she sits on will be unclean. 15:21 Anyone who touches her bed must wash his clothes, bathe in water, and be unclean until evening.

Leviticus 18:6

Laws of Sexual Relations

18:6 “‘No man is to approach any close relative to have sexual intercourse with her. I am the Lord.

Leviticus 18:20

18:20 You must not have sexual intercourse with the wife of your fellow citizen to become unclean with her.

Leviticus 21:3

21:3 and his virgin sister who is near to him, who has no husband; he may defile himself for her.