Under ordinary circumstances, if a married woman is raped, the halakha recognizes that the forbidden sexual act happened against her will and she remains permitted to her husband. A particularly painful situation arises if the woman who is raped is married to a kohen. In such a case halakha requires the couple to divorce, since as a kohen, the husband is not allowed to be married to a woman who has had a forbidden sexual encounter – which has happened to his wife, even though it was not her fault in any way.
Our Gemara quotes a teaching of Rav Sheshet, which says that if a married woman whose husband was not a kohen was raped, even though she can remain married to her husband, she cannot marry a kohen in the future, should she become widowed. This discussion revolves around the way the Sages define the term zona – one of the women that a kohen cannot marry (see Vayikra 21:7). Although the term zona usually is translated as a harlot – a woman who makes herself available to men for sexual pleasure – it is clear that the Sages did not understand the term in that way. As noted above, they defined a zona as a woman who has had a sexual encounter with someone who is forbidden to her – i.e. someone who she would theoretically be unable to marry. Nevertheless, this is a distinction to be made between an issur erva – an incestuous relationship, and eshet ish – an adulterous one. In the former case, the prohibition stems from the inherent personal status, the relationship between the two people; in the latter case the prohibition stems from the fact that she is married to another man, a personal choice that exists as long as the marriage does and can be undone by divorce or by the death of her husband.
Thus, the concept of zona, as applied to a married woman, is that of a woman who has abrogated the trust and relationship that existed between her and her husband. According to this line of reasoning, it appears reasonable to suggest that a married woman who was raped does not become a zona at all, since no trust was broken in such a case. Thus the Rashba argues that, were it not for Rav Sheshet’s ruling, we would have permitted a woman who was raped to marry a kohen, since she cannot be considered a zona.