Sotah 25A

ושמואל אמר: אנא דאמרי ⁠— אפילו לרבי יאשיה. מדאיצטריך קרא לרבויה ⁠— מכלל דלאו אשתו היא כלל.

And Shmuel could have said: I state my opinion even according to the opinion of R' Yoshiya. Since it was necessary for the verse to specifically include in the sota ritual a yevama who had sex with her yavam, by inference one may conclude that she is not his wife at all with regard to any matters other than those explicit in the verse.

איבעיא להו: עוברת על דת צריכה התראה להפסידה כתובתה, או אינה צריכה? מי אמרינן: כיון דעוברת על דת היא ⁠— לא בעיא התראה, או דלמא תיבעי התראה, דאי הדרה בה תיהדר בה?

§ A dilemma was raised before the rabbis: With regard to a woman who violates the precepts of halakha or Jewish custom with regard to modesty, who may be divorced without payment of her marriage contract, is forewarning from her husband required in order to cause her to forfeit her right to collect payment of her marriage contract or is forewarning not required? Do we say that since she is a woman who violates the precepts, forewarning is not required, as she is aware that her actions are prohibited? Or perhaps forewarning is required, so that if she desires to repent, she will be reminded to repent?

תא שמע: ארוסה ושומרת יבם לא שותות ולא נוטלות כתובה. מישתא הוא דלא שתיא, הא קנויי מקני לה. למאי? לאו להפסידה כתובתה?

The Talmud suggests: Come and hear a proof from the Mishnah: A betrothed woman and a widow awaiting her yavam neither drink the bitter water nor collect payment of their marriage contracts. It is possible to infer that she does not drink, but the husband or yavam can warn her against secluding herself with another man. For what halakha is his warning relevant? Is it not relevant to cause her to forfeit her right to collect payment of her marriage contract? Accordingly, a woman forfeits payment of her marriage contract due to immodest behavior only if she is warned.