Leviticus 18:10

Revised Standard Version (RSV-CI)

You shall not uncover the nakedness of your son's daughter or of your daughter's daughter, for their nakedness is your own nakedness.

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You shall not uncover the nakedness of your father's wife's daughter, begotten by your father, since she is your sister.

You shall not uncover the nakedness of your sister, the daughter of your father or the daughter of your mother, whether born at home or born abroad.