Nedarim 24A

״קונם שאיני נהנה לך אם אי אתה נוטל לבנך כור של חיטין ושתי חביות של יין״, הרי זה יכול להתיר את נדרו שלא על פי חכם, שיכול לומר לו: כלום אמרת אלא בשביל כבודי ⁠— זה הוא כבודי.

Benefiting from you is konam for me if you do not take from me for your son a kor of wheat and two jugs of wine as a gift, this other individual can dissolve his vow without the involvement of a halakhic authority. This is because he can say to the one who vowed: Did you say your vow for any reason other than due to my honor, in order to convince me to accept a gift for my son? This is my honor, that I refrain from accepting the gift.

טעמא דאמר ״זה הוא כבודי״, הא לאו הכי ⁠— נדר הוא. מני? אי רבי אליעזר בן יעקב ⁠— נדרי זירוזין הוי. אלא שמע מינה: פליגי רבנן עליה.

The Talmud infers: The reason that he may dissolve the vow without a halakhic authority is because the potential recipient said: This is my honor. But if he did not say so, then it is a vow. The Talmud clarifies: Whose opinion does this follow? If it is the opinion of R' Eliezer ben Ya’akov, then it is included in the category of vows of exhortation and is not considered a vow, since the intention was solely to encourage the other individual to accept the gift. Rather, conclude from this Mishnah that the Rabbis disagree with him and hold that vows of exhortation are also vows.

לעולם רבי אליעזר בן יעקב היא, ומודה רבי אליעזר בן יעקב בהאי דנדרא הוי, דאמר ליה: לא כלבא אנא, דמיתהנינא מינך ולא מיתהנית מינאי.

The Talmud responds: Actually, it is in accordance with the opinion of R' Eliezer ben Ya’akov, but R' Eliezer ben Ya’akov concedes in this case that it is a vow and not just a means of encouragement because the one who took the vow said to him: I am not a dog, that I benefit from you and you do not benefit from me. Therefore, one truly wants the vow to be valid so that the other will accept the gift, and it was not intended merely as a means of encouragement.