The Rebbe said, “Do not let a word of wickedness leave your mouth.” Do not say that you will commit a sin or be wicked, even though you may be joking and have no intention of carrying out your words. The words themselves can do great damage and later compel you to fulfill them. This is true even if they are uttered only as a joke.
It is written that King Jehu said, “Ahab served the Ba'al a little; Jehu will serve it much” (II Kings 10:18). These words were his downfall. When King Jehu said these words, he had absolutely no intention to commit idolatry. He only said this to trick the Ba'al worshippers, as explained in the next verse. Still, this was his downfall and he later committed idolatry.
The Talmud speaks about this and derives the lesson, “A covenant is made with the lips” (Sanhedrin 102a; Moed Katan 18a). Therefore, you should be very careful with what you say.
אָמַר: שֶׁצָּרִיךְ לִזָּהֵר מְאֹד לִבְלִי לְהוֹצִיא מִפִּיו דִּבּוּר שֶׁל רִשְׁעוּת ח"ו, אֲפִלּוּ בְּדֶרֶךְ לֵיצָנוּת. דְּהַיְנוּ שֶׁלֹּא לוֹמַר ח"ו עַל עַצְמוֹ 'שֶׁיִּהְיֶה רָשָׁע' ח"ו, אוֹ 'שֶׁיַּעֲשֶׂה עֲבֵרָה' ח"ו. אַף שֶׁאוֹמֵר זֹאת בְּדֶרֶךְ לֵיצָנוּת וְאֵין בְּלִבּוֹ כְּלָל לַעֲשׂוֹת זֹאת, אַף עַל פִּי כֵן זֶה הַדִּבּוּר מַזִּיק לוֹ מְאֹד וְיָכוֹל לְהַכְרִיחוֹ ח"ו אַחַר כָּךְ לַעֲשׂוֹת זֹאת שֶׁהוֹצִיא מִפִּיו, אַף עַל פִּי שֶׁלֹּא אֲמָרָהּ מִלִּבּוֹ רַק בְּדֶרֶךְ לֵיצָנוּת.
The Rebbe said, “Do not let a word of wickedness leave your mouth.” Do not say that you will commit a sin or be wicked, even though you may be joking and have no intention of carrying out your words. The words themselves can do great damage and later compel you to fulfill them. This is true even if they are uttered only as a joke.
וְעַל יְדֵי זֶה נִכְשַׁל יֵהוּא הַמֶּלֶךְ עַל יְדֵי שֶׁהוֹצִיא מִפִּיו וְאָמַר (מְלָכִים ב י־יח): "יֵהוּא יַעַבְדֶנּוּ הַרְבֵּה". אַף עַל פִּי שֶׁבְּלִבּוֹ הָיָה לִבְלִי לְעָבְדוֹ, רַק אָמַר זֹאת בְּדֶרֶךְ לֵיצָנוּת, כְּדֵי לְהַטְעוֹת אֶת עוֹבְדֵי הַבַּעַל (כַּמְבֹאָר שָׁם בַּמִּקְרָא), אַף עַל פִּי כֵן נִכְשַׁל אַחַר־כָּךְ עַל יְדֵי זֶה עַד שֶׁעָבַד בְּעַצְמוֹ עֲבוֹדָה זָרָה (כְּמוֹ שֶׁאָמְרוּ רַבּוֹתֵינוּ ז"ל).
It is written that King Jehu said, “Ahab served the Ba'al a little; Jehu will serve it much” (II Kings 10:18). These words were his downfall. When King Jehu said these words, he had absolutely no intention to commit idolatry. He only said this to trick the Ba'al worshippers, as explained in the next verse. Still, this was his downfall and he later committed idolatry.
עַל כֵּן צְרִיכִין לִזָּהֵר מִזֶּה מְאֹד כִּי בְּרִית כְּרוּתָה לַשְּׂפָתַיִם וְכוּ' (כְּמוֹ שֶׁאָמְרוּ רַבּוֹתֵינוּ ז"ל סַנְהֶדְרִין ק"ב. מוֹעֵד קָטָן י"ח).
The Talmud speaks about this and derives the lesson, “A covenant is made with the lips” (Sanhedrin 102a; Moed Katan 18a). Therefore, you should be very careful with what you say.