If one of the sisters was forbidden to one [of the brothers] under the prohibition of incest, he is forbidden to marry her but may marry her sister, while the second brother is forbidden to marry either of them. [If one sister] was forbidden due to a commandment or due to holiness they both perform halitzah and may not be taken in yibbum.

If one of the sisters was forbidden to one brother under the prohibition of incest and the other sister was forbidden to the other under the prohibition of incest, she who is forbidden to the one is permitted to the other and she who is forbidden to the other is permitted to the first. This is what they said: when her sister is her sister-in-law she may either perform halizah or be taken in yibbum.

Three brothers: two of whom were married to two sisters, or to a woman and her daughter, or to a woman and her daughter’s daughter, or to a woman and her son’s daughter, behold, these must perform halitzah but may not be taken in yibbum. Rabbi Shimon exempts them. If one of them was forbidden to him by a prohibition of incest, he is forbidden to marry her but is permitted to marry her sister. If the prohibition is due to a commandment or to holiness, they must perform halitzah but may not be taken in yibbum.

Three brothers, two of whom were married to two sisters and the third was unmarried: When one of the sisters’ husbands died, the unmarried brother performed for her ma’amar, and then his second brother died: Beth Shammai says: his wife [remains] with him while the other is exempt because she is his wife’s sister. Beth Hillel however says that he must divorce his wife with a get and by halitzah, and his brother’s wife by halitzah. This is the case in regard to which they said: “woe to him because of his wife, and woe to him because of his brother’s wife.”

Three brothers: two of whom were married to two sisters and the third was married to a stranger: If one of the sisters’ husbands died and the brother who was married to the stranger married his wife and then died himself, the first is exempt [from yibbum or halitzah] because she is his wife’s sister, and the second is exempt as her rival. If he had only had ma’amar with her and died, the stranger is to perform halitzah but may not be taken in yibbum. Three brothers: two of whom were married to two sisters and the third was married to a stranger: If the brother who was married to the stranger died, and one of the sisters’ husbands married his wife and then died himself, the first is exempt [from yibbum or halitzah] because she is his wife’s sister, and the second is exempt as her rival. If he had only had ma’amar with her and died, the stranger is to perform halitzah but may not be taken in yibbum.

Three brothers: two of whom were married to two sisters and the third was married to a stranger: If one of the sisters’ husband died and the brother who was married to the stranger married his wife, and then the wife of the second brother died, and afterwards the brother who was married to the stranger died, behold she is forbidden to him forever, since she was forbidden to him for one moment. Three brothers: two of whom were married to two sisters and the third was married to a stranger. If one of the sisters’ husbands divorced his wife, and then the brother who was married to the stranger died, and he who had divorced his wife married her and then died,- this is a case concerning which they said: If any of them died or were divorced, their rivals are permitted.

[If in any of these cases] the betrothal or divorce was in doubt, behold, these rivals must perform halitzah but may not be taken in yibbum. What is a case of doubtful betrothal? If when he threw to her betrothal money it was uncertain whether it fell nearer to him or nearer to her – this is a case of doubtful betrothal. [What is a case of] doubtful divorce? If he wrote a get in his own handwriting and it bore no signatures of witnesses, or if it bore signatures of witnesses but was note dated, or if it was dated but had the signature of only one witness this is a case of doubtful divorce.

Three brothers were married to three women who were strangers [to one another] and one of them died and the second brother did ma’amar with her and then he died, behold, these must perform halitzah but may not be taken in yibbum; for it is said “And one of them died…her husband’s brother shall unite with her” (Deuteronomy 25:5) only she who is bound due to one yavam but not she who is bound to due to two yavamim. R. Shimon says: he may have yibbum with whichever of these he wishes and then perform halitzah for the other. If two brothers were married to two sisters, and one of the brothers died, and afterwards the wife of the second brother died, behold, she is forbidden to him forever, since she was forbidden to him for one moment.

If two men betrothed two women, and as they were entering into the bridal chamber, they exchanged the one for the other, behold, they are guilty of having relations with a married woman. If they were brothers they are guilty of having relations with a brother’s wife. If they were sisters, they are guilty of having relations with a wife’s sister. If they were menstruants [they are guilty] of having relations with a menstruant. They must be kept apart for three months, lest they are pregnant. If they were minors incapable of bearing children, they may be returned [to their rightful husband] at once. If the women were of priestly families they are disqualified from eating terumah.