Gittin 84B

לאביי, ״כלל״⁠ – לאתויי בשר חזיר; ״כזה״⁠ – למעוטי פלוני.

And according to Abaye this principle was stated to include the case of a condition that she should eat pig meat, and the expression: A bill of divorce like this is a valid bill of divorce, serves to exclude a condition that she should have sex with so-and-so, in which case the divorce takes effect only once the condition is fulfilled, as it is possible to fulfill this condition in a permitted manner.

מיתיבי: ״הרי זה גיטיך על מנת שתאכלי בשר חזיר״; ואם היתה זרה ⁠– ״על מנת שתאכלי בתרומה״; ואם היתה נזירה ⁠– ״על מנת שתשתי יין״; נתקיים התנאי ⁠– הרי זה גט; ואם לאו ⁠– אינו גט. לרבא ניחא, לאביי קשיא!

The Talmud raises an objection from another baraita (Tosefta 6:10): If the husband said to his wife: This is your bill of divorce on the condition that you eat pig meat; or similarly, if she was a non-priestess, i.e., the daughter of an Israelite, and he stipulated: On the condition that you partake of teruma; or if she was a nazirite and he stipulated: On the condition that you drink wine (see Numbers 6:3); in all of these cases, if the condition is fulfilled it is a valid bill of divorce, and if not, it is not a valid bill of divorce. This works out well according to Rava, who holds that a condition that she should perform a forbidden act is binding; according to Abaye it is difficult.

אמר לך אביי: מי סברת דברי הכל היא?! הא מני ⁠– רבנן היא.

The Talmud answers that Abaye could have said to you: Do you hold that this ruling is agreed upon by everyone? That is not the case. Rather, in accordance with whose opinion is this baraita? It is in accordance with the opinion of the Rabbis, who disagree with R' Yehuda ben Teima, maintaining that even a condition that cannot be fulfilled is a valid condition.