Mishnà su Deuteronomio 25:5

These are subjects concerning which Beth Hillel changed their mind and taught according to the opinion of Beth Shammai:A woman who came from overseas and said: “My husband died” may be married again; “My husband died [without children]” she must be married by her husband’s brother (the levir). But Beth Hillel says: “We have heard so only in the case of one who came from the harvesting.” Beth Shammai said to them: “It is the same thing in the case of one who came from the harvesting or who came from the olive-picking or who came from overseas; they mentioned harvesting only because that is how it happened.” Then Beth Hillel changed their mind and taught according to Beth Shammai. Beth Shammai says: “She may be married again and take her kethubah payment.” But Beth Hillel says: “She may be married again but may not take her kethubah payment.” Beth Shammai said to them: “You have permitted the graver matter of a forbidden marriage, should you not permit the lighter matter of property?” Beth Hillel said to them: “We have found that brothers do not inherit on her statement.” Beth Shammai said to them: “Do we not infer it from her marriage document in which he writes to her ‘That if you be married to another you shall take what is written for you’?” Then Beth Hillel changed their mind and taught according to the opinion of Beth Shammai.

Beth Shammai permits the rival wives [of a deceased brother to be married] to the [surviving] brothers; But Beth Hillel forbids them. If they have performed halitzah, Beth Shammai pronounce them unfit to [marry into] the priesthood, But Beth Hillel pronounced them fit. If they have married their brother-in-law, Beth Shammai pronounce them fit [to marry into the priesthood], But Beth Hillel pronounced them unfit. And although these pronounce unfit and these pronounce fit, Beth Shammai did not refrain from marrying women from [the daughters of] Beth Hillel, nor did Beth Hillel refrain from marrying women from [the daughters of] Beth Shammai. And in the case of all matters of purity and impurity in respect to which these pronounce pure and these pronounce impure, they did not refrain from preparing foods requiring a condition of purity each by means of [the vessels of] the other.

[In the case of] three brothers, of whom two were married to two sisters and one was unmarried, if one of the husbands of the sisters died and the unmarried one betrothed her (maamar), and afterwards his other brother died, Beth Shammai says: his wife remains with him, and the other [widow] is released on the grounds of [the law forbidding] the wife’s sister. But Beth Hillel says: he should put away his wife with a get and halitzah, and the wife of his brother [he should put away] with halitzah. This is the case of which they said: woe to him because of his wife, and woe to him because of his brother’s wife!