יורה דעה רל״זYoreh De'ah 237

Se’if 1א׳

הָאוֹמֵר: אֲנִי נִשְׁבָּע שֶׁאֶעֱשֶׂה דָּבָר פְּלוֹנִי, אוֹ שֶׁלֹּא אֶעֱשֶׂנּוּ, הֲרֵי זֶה שְׁבוּעָה אַף עַל פִּי שֶׁלֹּא הִזְכִּיר לֹא שֵׁם וְלֹא כִּנּוּי. הַגָּה: וְאֵין חִלּוּק אִם הוֹצִיא הַשְּׁבוּעָה בִּלְשׁוֹן הַקֹּדֶשׁ אוֹ בְּכָל לָשׁוֹן שֶׁיֹּאמְרֶנָּה (תְּשׁוּבַת הָרַשְׁבָּ"א סִימָן תתמ"ב וּבְמָרְדְּכַי פ' שְׁבוּעוֹת שְׁתַּיִם וּבָרַמְבַּ"ם פי"ב מֵהִלְכוֹת שְׁבוּעוֹת).

One who says: I swear that I shall do such a thing, or that I shall not do it — behold this is an oath, even though he mentioned neither the Name nor a substitute name. Hagah [Rema]: And there is no difference whether he brought the oath out in the holy tongue or in any language in which he says it (a responsum of the Rashba, siman 842, and in Mordechai, chapter "Oaths, two", and in the Rambam, chapter 12 of the Laws of Oaths).

Se’if 2ב׳

הִשְׁבִּיעוֹ אַחֵר, שֶׁאָמַר לוֹ: אֲנִי מַשְׁבִּיעֲךָ שֶׁתַּעֲשֶׂה דָּבָר פְּלוֹנִי, אוֹ שֶׁלֹּא תַּעֲשֶׂנּוּ, וְעָנָה: אָמֵן, אוֹ דָּבָר שֶׁנִּשְׁמָע מִמֶּנּוּ שֶׁמְּקַבֵּל שְׁבוּעָתוֹ, כְּגוֹן שֶׁאָמַר: הֵן, אוֹ: קִבַּלְתִּי דְּבָרֶיךָ, הָוֵי כְּאִלּוּ נִשְׁבַּע בְּעַצְמוֹ. וַאֲפִלּוּ הִשְׁבִּיעוֹ עוֹבֵד כּוֹכָבִים אוֹ קָטָן.

Another imposed an oath upon him, in that he said to him: I impose an oath upon you that you shall do such a thing, or that you shall not do it, and he answered: Amen, or a thing from which it is heard that he accepts his oath, such as where he said: yes, or: I have accepted your words — it is as though he had sworn of himself. And even if an idolater or a minor imposed the oath upon him.

Se’if 3ג׳

אָמַר: אֱהֵא בְּאָלָה אוֹ בְּאָרוּר אִם לֹא אֶעֱשֶׂה דָּבָר פְּלוֹנִי, אוֹ שֶׁאָמַר לוֹ אַחַר כֵּן, וְקִבֵּל דְּבָרָיו, הָוֵי כִּשְׁבוּעָה אַף עַל פִּי שֶׁלֹּא הִזְכִּיר לֹא שֵׁם וְלֹא כִּנּוּי.

He said: I shall be under an imprecation, or under a curse, if I do not do such a thing; or where another said it to him afterwards and he accepted his words — it is as an oath, even though he mentioned neither the Name nor a substitute name.