You must not have sexual relations with the sister of your mother or your father, for it is exposing one’s own kin; both shall bear their iniquity.
Jewish Publication Society of America Version (JPS1917) - Leviticus 20:19 >And thou shalt not uncover the nakedness of thy mother's sister, nor of thy father's sister; for he hath made naked his near kin; they shall bear their iniquity.