עֶרְוַ֥ת אֲחֽוֹת־אִמְּךָ֖ לֹ֣א תְגַלֵּ֑ה כִּֽי־שְׁאֵ֥ר אִמְּךָ֖ הִֽוא׃ (ס)
Thou shalt not uncover the nakedness of thy mother’s sister; for she is thy mother’s near kinswoman.
Read kabbalistic (mystical) interpretation of Leviticus 18:13: and classical mystical sources.