חמש עשרה נשים פוטרות צרותיהן וצרות צרותיהן מן החליצה ומן הייבום עד סוף העולם.
The Torah law obligating a man whose brother died without children [yavam] to marry his deceased brother’s widow [yevama] or to free her from her levirate bonds through the act of ḥalitza applies only when it is permitted for the widow to marry her surviving brother-in-law. However, in cases where the yevama is forbidden to her yavam due to her status as a close family relative, the mitzva of levirate marriage is not applicable, and she is exempt from both levirate marriage and ḥalitza. The rabbis further taught that the exemption of a yevama from levirate marriage also exempts her rival wife. In other words, if the deceased brother had two wives, each a so-called rival of the other, and only one wife is a relative of the surviving brother, then the rival wife is also exempt from both levirate marriage and ḥalitza. Moreover, if that same rival wife entered into levirate marriage with a different brother of the deceased, one to whom she is not forbidden, then were this third brother also to die childless, so that the obligation of levirate marriage would again be incurred by the second brother, not only is the forbidden rival wife exempt from levirate marriage and ḥalitza, her new rival wives from her second marriage are also exempt. That is to say, any other wife of the third brother is exempt from the mitzva of levirate marriage, as she is the rival wife of that first rival wife, who was exempted from levirate marriage following her first husband’s death due the exemption of her original rival wife. The same principle applies if that second rival wife subsequently enters into levirate marriage with another permitted brother, and so on. In summary, every widow who is exempt from marrying her brother-in-law due to her status as rival wife of a forbidden relative is treated as a forbidden relative herself and is therefore exempt from both ḥalitza and levirate marriage and causes exemption for future rival wives as well. Mishnah: The Mishnah describes various cases that invoke the principles above. 15 categories of women constitute familial sex that are forbidden as incestuous, and consequently, these women exempt their rival wives and the rival wives of their rival wives from ḥalitza and from levirate marriage forever, i.e., they also exempt rival wives of rival wives of rival wives, and so on.