וְעֶרְוַ֨ת אֲח֧וֹת אִמְּךָ֛ וַאֲח֥וֹת אָבִ֖יךָ לֹ֣א תְגַלֵּ֑ה כִּ֧י אֶת־שְׁאֵר֛וֹ הֶעֱרָ֖ה עֲוֺנָ֥ם יִשָּֽׂאוּ׃
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.
Read kabbalistic (mystical) interpretation of Leviticus 20:19: and classical mystical sources.