עֶרְוַ֥ת אֲחוֹת־אָבִ֖יךָ לֹ֣א תְגַלֵּ֑ה שְׁאֵ֥ר אָבִ֖יךָ הִֽוא׃ (ס)
Thou shalt not uncover the nakedness of thy father’s sister: she is thy father’s near kinswoman.
Read kabbalistic (mystical) interpretation of Leviticus 18:12: and classical mystical sources.