Why does Leviticus mention both father and mother in this prohibition? It reveals a deeper truth about the married couple's bond.
The verse prohibits uncovering the 'nakedness' of your father or mother. While this immediately brings to mind a son having relations with his mother, or a daughter with her father, the wording is intentionally layered.
One Flesh, One Prohibiction
The text emphasizes the profound unity of a married couple, calling them 'one flesh' in Genesis 2:24. Because of this sacred union, the prohibition against uncovering a parent's nakedness extends to both. As commentators note, the 'nakedness of the father' and the 'nakedness of the mother' are treated as fundamentally the same thing in the context of incest.
This unity means that the stepmother, who becomes 'one flesh' with the father through marriage, is also included in this prohibition (Leviticus 18:8). The bond created by marriage is as significant as the bond of blood, and violating it with a family member brings serious consequences.