עֶרְוַ֨ת אֲחֽוֹתְךָ֤ בַת־אָבִ֙יךָ֙ א֣וֹ בַת־אִמֶּ֔ךָ מוֹלֶ֣דֶת בַּ֔יִת א֖וֹ מוֹלֶ֣דֶת ח֑וּץ לֹ֥א תְגַלֶּ֖ה עֶרְוָתָֽן׃ (ס)
La nudità di tua sorella, la figlia di tuo padre o la figlia di tua madre, che sia nata a casa o nata all'estero, non scoprirai nemmeno la loro nudità. .
Shenei Luchot HaBerit
We are to understand the words: מולדת ביתאו מולדת חוץ in 18,9 as an allusion to two "sister-like" emanations, i.e. בינה and גבורה. [This emanation is also referred to as דין, and is on the "left" side of the diagram, immediately beneath that of בינה. Ed.] These two emanations are perceived as each having another "sister" emanation i.e. הוד ומלכות. If someone indulges in sexual intercourse with a granddaughter (daughter of his daughter), he inflicts damage on the equilibrium in the emanation הוד, which is perceived as a "daughter" of the emanation גבורה, whereas if he indulges in intercourse with a granddaughter who is the daughter of his son, he disturbs the equilibrium in the domain of the emanation מלכות, which is perceived as the daughter of the emanation נצח.