Bava Batra 120B

״זה הדבר״ דראשי המטות ⁠– הכי נמי דלא יהא נוהג אלא בדור זה? אמר ליה: ההוא, יליף ״זה״–״זה״ מהתם.

Rabba Zuti asked Rav Ashi about another instance of the same phrase. In the case of “this is the matter” written with regard to the heads of the tribes, in the introductory verse to the halakhot of vows: “And Moses spoke to the heads of the tribes of the children of Israel, saying: This is the matter that YHWH has commanded” (Numbers 30:2), is it also the case that the halakhot of vows will not be practiced except in this generation? Rav Ashi said to him: The halakha in that case, that of vows, is derived through a verbal analogy between the word “this” stated here, in the verse discussing vows, and the word “this” stated there, in the verse discussing offerings slaughtered outside the Tabernacle or Temple, which is applicable in all generations.

האי נמי, ליליף ״זה״–״זה״ מהתם! האי מאי? בשלמא התם, איצטריך לגזרה שוה; הכא ⁠– למאי איצטריך? לשתוק קרא מיניה, ואנא ידענא דלדורות הוא!

The Talmud asks: This halakha, concerning the daughter inheriting her father’s portion, let it be derived through a verbal analogy between the word “this” stated here, with regard to inheritance, and the word “this” stated there, in the verse discussing offerings, as well. The Talmud rejects that comparison: What is this suggestion? Granted, there, i.e., with regard to offerings slaughtered outside the Tabernacle or Temple and with regard to vows, the phrase “this is the matter” was necessary for deriving other halakhot through a verbal analogy, as will be explained later. Therefore, the term may also be employed to teach that the halakha applies in all generations. But here, with regard to a daughter’s inheritance, for what other halakha was this phrase necessary? If the halakha truly applies for posterity, let the verse be silent and refrain from addressing when this halakha applies by not stating “this is the matter,” and I would know that it is for all generations, as is the case with all other mitzvot.