Mishnayos Kerisos Perek 3 Mishnah 6

משום חמותו וכלתו ואחות אשתו (because of his mother-in-law, his daughter-in-law and his wife’s sister) – the father who had sexual intercourse with his daughter and produced from her a daughter, Reuven married this daughter, her mother is prohibited to him because she is his mother-in-law and [because] she is his wife’s sister; If she married the son of Reuven, there is added to her the prohibition because of his daughter-in-law. If the son of Reuven died, or he divorced her and she married his brother, there is added to her the prohibition of being the wife of his brother. If his brother dies or he divorced her and she married his father’s brother, there is added to her the prohibition of being the wife of his father’s brother. If she merely married and she is a married woman and is menstruating. If Reuven had sexual relations with her while she was married and a menstruating woman, he is liable for her because of all of these prohibitions listed by name.

וכן הבא על אם חמותו – Laban has sexual relations with Dinah, the daughter of Leah his daughter, and he sires a daughter, whose name is Serah; the person (i.e., man) who marries Serah is forbidden to Leah because of the mother of his mother-in-law and because she is the sister of his wife, for Serah his wife and Leah are the daughters of Laban. If Leah is married to the daughter of the husband of Serah,, and becomes his daughter-in-law, and afterwards to his brother, and afterwards to the brother of his father, if the husband of Serah has sexual relations while she is a married woman and a menstruating woman, he is liable for her because of all of the categories mentioned.

ואם חמיו – Reuven has sexual relations with his grandmother, the wife of Laban, the mother of his mother Leah, and he sires a daughter and her name is Dinah, the person who marries Dinah will be forbidden to Leah, the mother of Reuven will be forbidden to him because of [the prohibition] of the mother of his father-in-law and because of the [prohibition] of the sister of his wife, for Dinah, his wife, and Leah, the mother of his father-in-law, both of them are the daughters of the wife of Laban. If she became his daughter-in-law and afterwards the wife of his brother and afterwards the wife of his father’s brother and a married woman and a menstruating woman, he is liable for her because of all of these categories mentioned.

הבא על חמותו חייב עליה כו' – The wife of Laban had two daughters, Leah and Rachel, and one son, whose name is Asher, and the name of Asher’s daughter is Serah, and one came from the marketplace and married Rachel and Yocheved the daughter of Leah and Serah the daughter of Asher, and afterwards, the person who marries these three women has sexual relations with the wife of Laban, he is liable on her account because of his mother-in-law, and the mother of his mother-in-law, and the mother of his father-in-law. Because of his mother-in-law, for she is the mother of Rachel his wife. And because of the mother of his mother-in-law, for she is the mother is Leah his mother-in-law. And because of the mother of his father-in-law, because she is the mother of Asher his father-in-law.

שלשתן שם אחד הם – in one Biblical verse it is written (see Leviticus 18:17 – “Do not uncover the nakedness of a woman and her daughter; nor shall you marry her son’s daughter or her daughter’s daughter and uncover her nakedness: they are kindred; it is depravity”) and one it is not. Therefore, there is no separation of sin-offerings between them. And this is the Halakha (i.e., only one sin-offering).