Bava Batra 130A

וקדושין.

and betrothal, as if a man betroths a woman and retracts the betrothal within the time required for speaking, his retraction is not effective.

מתני׳ האומר ״איש פלוני יירשני״ במקום שיש בת; ״בתי תירשני״ במקום שיש בן ⁠– לא אמר כלום, שהתנה על מה שכתוב בתורה. רבי יוחנן בן ברוקה אומר: אם אמר על מי שראוי ליורשו ⁠– דבריו קיימין; ועל מי שאין ראוי לו ליורשו ⁠– אין דבריו קיימין.

Mishnah: In a case of one who says: So-and-so will inherit from me, in a case where there is a daughter, or: My daughter will inherit from me, in a case where there is a son, he has said nothing, as he has stipulated counter to that which is written in the Torah concerning the order of inheritance. R' Yoḥanan ben Beroka says: If he said this about one fit to inherit from him, his statement stands, but if it was about one for whom it was not fit to inherit from him, his statement does not stand.

גמ׳ טעמא דאחר במקום בת, ובת במקום בן; הא בן בין הבנים, ובת בין הבנות ⁠– דבריו קיימין. אימא סיפא, רבי יוחנן בן ברוקה אומר: אם אמר על מי שראוי ליורשו ⁠– דבריו קיימין. היינו תנא קמא!

Talmud: The Talmud infers from the Mishnah that the reason the first tanna rules that his bequeathal is invalid is that he bequeathed his estate to another in a case where he had a daughter, or to his daughter where he had a son, but if he bequeathed his entire estate to one son among his other sons, or to one daughter among his other daughters, his statement stands. The Talmud questions this inference: Say the latter clause of the Mishnah: R' Yoḥanan ben Beroka says that if he said this about one fit to inherit from him, his statement stands. This is identical to the opinion of the first tanna. What information does this statement of R' Yoḥanan ben Beroka add? With regard to what case do they disagree?