Gittin 82B

שרבי אליעזר מתיר לכל אדם חוץ מאותו האיש, וחכמים אוסרים.

as in this case R' Eliezer permits her to marry any man except for that man about whom the condition was made, and the Rabbis prohibit her from remarrying, as in their opinion this divorce is not valid.

מאי טעמא דרבי אליעזר? מידי דהוה אכל תנאי דעלמא. ורבנן ⁠– כל תנאי דעלמא לא שייר ליה בגט, הכא שייר לה בגט.

The Talmud asks: What is the reasoning behind R' Eliezer’s opinion as cited in the baraita? The Talmud answers: The ruling here is just as it is with regard to any typical condition. The husband has the right to attach conditions to the divorce. And how would the Rabbis respond to this reasoning? They would reason that by attaching any typical condition the husband did not leave out part of the bill of divorce, as it does not diminish the essential act of severance. By contrast, here he left out part of the bill of divorce, as she is not permitted to marry any man she wishes. Therefore, the divorce is invalid.

ומתניתין ⁠– דאוקימנא ב״חוץ״, מאי טעמא דרבי אליעזר?

The Talmud asks: And according to the Mishnah, which we established as referring to a case of exception, what is the reason for R' Eliezer’s opinion that the divorce takes effect, despite its lack of complete severance?

אמר רבי ינאי משום זקן אחד, אמר קרא: ״ויצאה מביתו והלכה והיתה לאיש אחר״⁠ – אפילו לא התירה אלא לאיש אחר, הרי זו מגורשת. ורבנן אמרי, טעמא דרבי אליעזר: האי ״איש״⁠ – לכל איש ואיש.

R' Yannai said in the name of one elder that the verse states with regard to divorce: “And she departs out of his house, and goes and becomes another man’s wife” (Deuteronomy 24:2), indicating that even if he divorced her in a manner that only permitted her to marry one other man, she is divorced, i.e., this partial severance takes effect. And the Rabbis would say in response to R' Eliezer’s explanation that this phrase: Another man, which appears in the verse refers not to a specific man but to any man, i.e., it must be permitted for her to marry any man for the divorce to take effect.