Nedarim 78A

״זה הדבר״⁠ — חכם מתיר, ואין בעל מתיר. תניא אידך: ״זה הדבר״⁠ — בעל מפר ואין חכם מפר. שיכול: ומה בעל שאין מתיר ⁠— מפר, חכם שמתיר ⁠— אינו דין שמפר, תלמוד לומר: ״זה הדבר״⁠ — בעל מפר, ואין חכם מפר.

“This is the thing” (Numbers 30:2), to teach that the husband nullifies vows and a halakhic authority dissolves vows, but a husband does not dissolve them. It is taught in another baraita: The phrase “this is the thing” teaches that a husband nullifies vows but a halakhic authority does not nullify vows. As, one might have thought: Just as a husband, who cannot dissolve vows, nevertheless nullifies them, so too with regard to a halakhic authority, who can dissolve vows, is it not logical that he should also nullify them? Therefore, the verse states: “This is the thing,” to teach us that a husband nullifies vows, but a halakhic authority does not nullify them.

נאמר כאן ״זה הדבר״, ונאמר להלן ״זה הדבר״ בשחוטי חוץ. מה בשחוטי חוץ ⁠— אהרן ובניו וכל ישראל, אף פרשת נדרים ⁠— אהרן ובניו וכל ישראל. ומה כאן ראשי המטות ⁠— אף להלן ראשי המטות.

It is taught in a baraita: It is stated here, with regard to vows: “This is the thing,” and it is stated elsewhere: “Speak to Aaron, and to his sons, and to all the children of Israel, and say to them: This is the thing which YHWH has commanded, saying” (Leviticus 17:2), in the verse introducing the prohibition against slaughtering offerings outside of the Temple courtyard. Just as with regard to offerings slaughtered outside the Temple courtyard, the verse is directed to Aaron and his sons and all of Israel, so too, the portion in the Torah about vows is directed to Aaron and his sons and all of Israel. And just as here, with regard to vows, the verse states: “And Moses spoke to the heads of the tribes of the children of Israel” (Numbers 30:2), so too, there, with regard to offerings slaughtered outside the Temple courtyard, Moses spoke to the heads of the tribes.