Mishnayos Nedarim Perek 8 Mishnah 7

In the case of one who says to another: Benefiting from you is konam for me, i.e., I am prohibited from deriving benefit from you, if you do not come and take for your son one kor of wheat and two barrels of wine as a gift, this other individual can dissolve his vow without the consent of a halakhic authority. This is because he can say to him: 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, and consequently the vow is annulled. And, so too, in the case of one who says to another: Benefiting from me is konam for you, i.e., you are prohibited from deriving benefit from me, if you do not come and give my son one kor of wheat and two barrels of wine, Rabbi Meir says: It is prohibited for the other individual to benefit from the speaker until he gives the gifts to his son. However, the Rabbis say: Even this individual who took the vow can dissolve his own vow without the consent of a halakhic authority. This is because he can say to him: I hereby consider it as though I have received the gift. If an individual was urging another to marry the daughter of his sister, and in order to deflect the pressure, the other man said: Benefiting from me is konam for her forever, i.e., she is prohibited from deriving any benefit from me forever, and, so too, if there is one who divorces his wife and says: Benefiting from me is konam for my wife forever, these women are permitted to derive benefit from him, as this man intended to take this vow only for the purpose of prohibiting marriage between them, but not to prohibit all forms of benefit. Similarly, if one was urging another to eat with him, and the latter said: Entering your house is konam for me, as is tasting even a drop of cold liquid of yours, the individual who took the vow is nevertheless permitted to enter his house and to drink a cold beverage of his. This is because this individual intended to take this vow only for the purpose of eating and drinking a meal, but not to prohibit himself from entering the house entirely or from drinking in small quantities (Commentary on Nedarim).

הָאוֹמֵר לַחֲבֵרוֹ קוֹנָם שֶׁאֲנִי נֶהֱנֶה לְךָ אִם אֵין אַתָּה בָא וְנוֹטֵל לְבָנֶיךָ כּוֹר אֶחָד שֶׁל חִטִּין וּשְׁתֵּי חָבִיּוֹת שֶׁל יַיִן, הֲרֵי זֶה יָכוֹל לְהָפֵר אֶת נִדְרוֹ שֶׁלֹּא עַל פִּי חָכָם, וְיֹאמַר לוֹ, כְּלוּם אָמַרְתָּ אֶלָּא מִפְּנֵי כְבוֹדִי, זֶהוּ כְבוֹדִי. וְכֵן הָאוֹמֵר לַחֲבֵרוֹ קוֹנָם שֶׁאַתָּה נֶהֱנֶה לִי אִם אֵין אַתָּה בָא וְנוֹתֵן לִבְנִי כּוֹר אֶחָד שֶׁל חִטִּין וּשְׁתֵּי חָבִיּוֹת שֶׁל יַיִן, רַבִּי מֵאִיר אוֹמֵר, אָסוּר עַד שֶׁיִּתֵּן. וַחֲכָמִים אוֹמְרִים, אַף זֶה יָכוֹל לְהָפֵר אֶת נִדְרוֹ שֶׁלֹּא עַל פִּי חָכָם, וְיֹאמַר לוֹ, הֲרֵי אֲנִי כְאִלּוּ הִתְקַבָּלְתִּי. הָיוּ מְסָרְבִין בּוֹ לָשֵׂאת בַּת אֲחוֹתוֹ וְאָמַר קוֹנָם שֶׁהִיא נֶהֱנֵית לִי לְעוֹלָם, וְכֵן הַמְגָרֵשׁ אֶת אִשְׁתּוֹ וְאָמַר קוֹנָם אִשְׁתִּי נֶהֱנֵית לִי לְעוֹלָם, הֲרֵי אֵלּוּ מֻתָּרוֹת לֵהָנוֹת לוֹ, שֶׁלֹּא נִתְכַּוֵּן זֶה אֶלָּא לְשׁוּם אִישׁוּת. הָיָה מְסָרֵב בַּחֲבֵרוֹ שֶׁיֹּאכַל אֶצְלוֹ, אָמַר קוֹנָם לְבֵיתְךָ שֶׁאֵינִי נִכְנָס, טִפַּת צוֹנֵן שֶׁאֵינִי טוֹעֵם לָךְ, מֻתָּר לִכָּנֵס לְבֵיתוֹ וְלִשְׁתּוֹת מִמֶּנּוּ צוֹנֵן, שֶׁלֹּא נִתְכַּוֵּן זֶה אֶלָּא לְשׁוּם אֲכִילָה וּשְׁתִיָּה: