He prohibited us from sexual intercourse with a woman and her daughter. And that is His, may He be blessed, saying, "The nakedness of a woman and her daughter you shall not uncover" (Leviticus 18:17). And one who transgresses this negative commandment volitionally - and that is when one of them is his wife and he has sexual intercourse with the other - is liable for burning. But if the testimony was not ratified, it is with excision if it was volitional. And if he was inadvertent, he must sacrifice a fixed sin-offering.