Keritot, Chapter Three, Mishnah Six
Todays mishnah is a continuation of yesterdays mishnah. There are more attempts to figure out how many transgressions a person can transgress with one act of intercourse.
1) If one had relations with his mother-in-law he may thereby become guilty for [having relations] with his mother-in-law, his daughter-in-law, his brother’s wife, the wife of his father’s brother, his wife’s sister, a married woman, and a menstruant.
2) And so too, if one had intercourse with the mother of his father-in-law or of his mother-in-law.
3) Rabbi Yohanan ben Nuri said: if one had intercourse with his mother-in-law he may thereby become guilty for [having relations] with his mother-in-law, the mother of his mother-in-law, and the mother of his father-in-law.
a) They said to him: all these three are the same name.
Section one: Ill use some names for this one. Lets say Lavan has sex with Leah his daughter and they have a daughter, Dina. Yaakov marries Dina, so that Leah is his mother-in-law and his wifes sister. Leah marries Reuven, Yaakovs son, and now Leah is his daughter-in-law. If Reuven dies or divorces her and then she marries Yaakovs brother, she is now his brothers wife. Then, after death or divorce, she marries Yaakovs fathers brother, so she is his fathers brothers wife. If she is married and a menstruant when Yaakov has relations with her, he is liable for seven hatats.
Section two: One can become liable for the same hatats if the woman is the mother of his father-in-law or the mother of his mother-in-law.
Section three: Eve has two daughtersRachel and Leah and one son, Lavan. If Yaakov marries Rachel and Leahs daughter and Lavans daughter, then Eve is his mother-in-law (Rachels mother), his mother-in-laws mother-in-law (Leahs daughters mother) and his father-in-laws mother (Lavan, his father-in-laws, mother). If you added these prohibitions to the previous scenario, you could come up with nine hatats (dont try this at home!).
The other rabbis say that mother-in-laws are all one name, meaning that they are all one prohibition. This is because the prohibition of various types of mother-in-laws is included in Leviticus 18:17: Do not uncover the nakedness of a woman and her daughter; nor shall you marry her sons daughter or her daughters daughter and uncover her nakedness: they are kindred, it is depravity. Since they are all included in one verse if someone manages to have a woman who is all three at the same time, there is only one hatat for the mother-in-law prohibitions.