에스겔 16:7의 Halakhah

"And numerous" - as it is stated (Ezekiel 16:7), "I have given you to be numerous as the vegetation of the field, and you increased and grew and became highly ornamented, your breasts were set and your hair grew, but you were naked and barren;" "And I passed over you and I saw you wallowing in your blood, and I said to you, 'You shall live in your blood,' and I said to you, 'You shall live in your blood'" (Ezekiel 16:6).

To hug or kiss one of the arayos whom people do not normally lust after, such as his adult sister or his aunt or similar, even though he derives no pleasure at all, is very reprehensible, forbidden, and the act of a fool. This is because there are no relatives for [the purposes of] licentiousness at all, whether adult or minor, except the father to his daughter and the mother to her son. How is this? A father is permitted to hug his daughter, kiss her, and sleep next to her with flesh touching, and so too a mother with her son, as long as they are minors. When they grow up, so that the son is an adult, and the daughter is an adult until "her breasts are formed and her hair grows" (Ezekiel 16:7), they must sleep clothed. If the daughter is embarrassed to stand before her father naked, or she is betrothed, and likewise if the mother is embarrassed to stand before her son naked – even if they are minors, when they reach the point of being embarrassed, they may not sleep together except clothed.