You shall not take the name of the LORD your God in vain (Exodus 20:7); (see Pesikta Rabbati there). Anyone who recites a blessing that is not needed transgresses on account of you shall not take in vain. When Rav Dimi came, he said in the name of Rabbi Yochanan: I will eat and I will not eat, this is a false oath, and its prohibition is from you shall not swear by My name falsely (Leviticus 19:12). I ate and I did not eat, this is a vain oath, and its prohibition is from here: you shall not take the name of the LORD your God in vain. As for vows of forbidding, one who violates them transgresses he shall not break his word (Numbers 30:3). They raised an objection: vain and false are one thing. Is it not that, just as vain refers to the past, false too refers to the past, so that I ate and I did not eat is false? No, this case is as it is and that case is as it is. And what is meant by they are one thing? That they were said in a single utterance, as it was taught: Remember and Keep were said in a single utterance, something the mouth cannot speak and the ear cannot hear. Granted there, they were said in a single utterance, as Rav Adda bar Ahavah said: women are obligated in the sanctification of the day by Torah law, for Scripture says Remember and Keep; whoever is included in keeping is included in remembering, and these women, since they are included in keeping, are also included in remembering. But here, for what law is it needed? Rather, just as one is flogged for a vain oath, so one is flogged for a false oath. That is obvious, this is a negative commandment and that is a negative commandment! Lest you say, as Rav Papa said to Abaye, He will not hold guiltless at all, it teaches us as he answered him. And if you wish, say: just as one brings a sacrifice for a false oath, so one brings a sacrifice for a vain oath, and this is the view of Rabbi Akiva, who holds one liable for the past as for the future. When Ravin came, he said in the name of Rabbi Yirmiyah in the name of Rabbi Abbahu in the name of Rabbi Yochanan: I ate and I did not eat is a matter of falsehood, and its prohibition is from you shall not swear by My name falsely. I will eat and I will not eat, one transgresses he shall not break his word. And which is the vain oath? One who swears to alter a known fact.
Taking God's Name in Vain and the False and Vain Oath
Yalkut Shimoni on Torah 293:1
(שמות כ ז) לֹא תִשָּׂא אֶת שֵׁם ה' אֱלֹהֶיךָ, (פְּסִיקְתָּא רַבָּתִי עַיֵּן שָׁם). כָּל הַמְּבָרֵךְ בְּרָכָה שֶׁאֵינָהּ צְרִיכָה עוֹבֵר מִשּׁוּם לֹא תִשָּׂא. כִּי אָתָא רַב דִּימֵי אָמַר רַבִּי יוֹחָנָן אוֹכַל וְלֹא אוֹכַל, שֶׁקֶר, וְאַזְהָרָתֵהּ (ויקרא יט, יב) מִ"וְּלֹא תִשָּׁבְעוּ בִשְׁמִי לַשֶּׁקֶר", אָכַלְתִּי וְלֹא אָכַלְתִּי, שָׁוְא, וְאַזְהָרָתֵהּ מֵהָכָא לֹא תִשָּׂא אֶת שֵׁם ה' אֱלֹהֶיךָ לַשָּׁוְא, קוֹנָמוֹת עוֹבֵר (במדבר ל, ג) "בְּלֹא יַחֵל דְּבָרוֹ". מֵיתֵיבֵי שָׁוְא וָשֶׁקֶר אֶחָד הֵן, מַאי לָאו מִדְּשָׁוְא לְשֶׁעָבַר שֶׁקֶר נַמֵי לְשֶׁעָבַר, אַלְמָא אָכַלְתִּי וְלֹא אָכַלְתִּי שֶׁקֶר הוּא. לֹא, הָא כִּדְאִיתָא וְהָא כִּדְאִיתָא. וּמַאי דָּבָר אֶחָד הֵן, דִּבְדִבּוּר אֶחָד נֶאֶמְרוּ, כִּדְתַּנְיָא "זָכוֹר וְשָׁמוֹר" בְּדִבּוּר אֶחָד נֶאֶמְרוּ, מַה שֶּׁאֵין הַפֶּה יָכוֹל לְדַבֵּר וּמַה שֶּׁאֵין הָאֹזֶן יְכוֹלָה לִשְׁמֹעַ. בִּשְׁלָמָא הָתָם בְּדִבּוּר אֶחָד נֶאֶמְרוּ כִּדְרַב אַדָּא בַּר אַהֲבָה דַּאֲמַר, נָשִׁים חַיָּבוֹת בְּקִדּוּשׁ הַיּוֹם דְּבַר תּוֹרָה, דְּאָמַר קְרָא "זָכוֹר וְשָׁמוֹר", כָּל שֶׁיֶּשְׁנוֹ בִּשְׁמִירָה יֶשְׁנוֹ בִּזְכִירָה, וְהַנֵי נָשֵׁי הוֹאִיל וְאִיתְנָהוּ בִּשְׁמִירָה אִיתְנָהוּ נַמִּי בִּזְכִירָה, אֶלָּא הָכָא לְמַאי הִלְכְתָא מִבַּעְיָא לֵיהּ, אֶלָּא כְּשֵׁם שֶׁלּוֹקֶה עַל (שֶׁקֶר) [שָׁוְא] כָּךְ לוֹקֶה עַל (שָׁוְא) [שֶׁקֶר]. פְּשִׁיטָא הַאי לָאו וְהַאי לָאו. מַהוּ דְּתֵימָא כִּדְאָמַר לֵיהּ רַב פָּפָּא לְאַבַּיֵּי לֹא יְנַקֶּה כְּלָל, קָא מַשְׁמַע לָן כִּדְשַׁנִי לֵיהּ, וְאִי תֵּימָא כְּשֵׁם שֶׁמֵּבִיא קָרְבָּן עַל שֶׁקֶר כָּךְ מֵבִיא קָרְבָּן עַל שָׁוְא, וְרַבִּי עֲקִיבָא הִיא דִּמְחַיֵּב לְשֶׁעָבַר כִּלְהַבָּא. כִּי אָתָא רָבִין אָמַר רַבִּי יִרְמִיָּה אָמַר רַבִּי אַבָּהוּ אָמַר רַבִּי יוֹחָנָן, אָכַלְתִּי וְלֹא אָכַלְתִּי דְּבַר שֶׁקֶר, וְאַזְהָרָתֵהּ מִ"וְּלֹא תִשָּׁבְעוּ בִּשְׁמִי לַשָּׁקֶר", אוֹכַל וְלֹא אוֹכַל עוֹבֵר (במדבר ל, ג) "בְּלֹא יָחֵל דְּבָרוֹ", וְאֵי זֶה שְׁבוּעַת שָׁוְא, נִשְׁבָּע לְשַׁנּוֹת אֶת הַיָּדוּעַ.