Halacha

הלכה א
אֶחָד הַנִּשְׁבָּע אֶחָד מֵאַרְבָּעָה מִינֵי שְׁבוּעוֹת אֵלּוּ מִפִּי עַצְמוֹ. וְאֶחָד הַמֻּשְׁבָּע מִפִּי אֲחֵרִים וְעָנָה אָמֵן. אֲפִלּוּ הִשְׁבִּיעוֹ עַכּוּ''ם אוֹ קָטָן וְעָנָה אָמֵן חַיָּב. שֶׁכָּל הָעוֹנֶה אָמֵן אַחַר שְׁבוּעָה כְּמוֹצִיא שְׁבוּעָה מִפִּיו. וְאֶחָד הָעוֹנֶה אָמֵן אוֹ הָאוֹמֵר דָּבָר שֶׁעִנְיָנוֹ כְּעִנְיַן אָמֵן. כְּגוֹן שֶׁאָמַר הֵן אוֹ מְחֻיָּב אֲנִי בִּשְׁבוּעָה זוֹ. קִבַּלְתִּי עָלַי שְׁבוּעָה זוֹ. וְכָל כַּיּוֹצֵא בָּזֶה בְּכָל לָשׁוֹן הֲרֵי זֶה כְּנִשְׁבָּע לְכָל דָּבָר בֵּין לְחַיְּבוֹ מַלְקוֹת בֵּין לְחַיְּבוֹ קָרְבָּן:
כסף משנה
1.
Whether one takes one of these four oaths [falsely] on his own initiative or he is placed under oath by another person and answers Amen to his statements, he is liable.1The concept that a person is considered to have taken an oath when he responds Amen to the statements is derived from the Torah's statements with regard to a sotah, a woman suspected of adultery (Numbers 5:22 . For she is required to answer Amen to the oath administered to her by the priest and yet, it is considered as if she took the oath herself. [This applies] even if he is placed under oath by a gentile2Although in most instances, statements made by gentiles are of no significance according to Jewish Law, this is an exception. Here also there is an allusion to this concept in the Torah itself. Ezekiel 17:13 and II Chronicles 36:13 speak of Nebuchadnetzar having King Tzidkayahu take an oath. Nedarim 65a states that this oath was binding. Similarly, Sh'vuot 36a speaks of an oath Moses took to Jethro, his gentile father-in-law (Kessef Mishneh). or a minor3This is derived through a comparison to gentiles. and responds Amen.
[The rationale is that] anyone who responds Amen or makes a statement equivalent to responding Amen, e.g., he says "Yes," "I am obligated in this oath," "I accept this oath upon myself," or the like in any language4I.e., not only in lashon hakodesh, the Hebrew used in the Bible and by the Sages. is considered to have taken an oath with regard to all matter,5See Chapter 7, Halachah 1, Chapter 8, Halachah 7, and Chapter 9, Halachah 1, which mentions instances where a person is considered to have taken an oath even if he does not respond Amen. whether it be liability for lashes6If he takes a false sh'vuat bitui or takes an oath in vain. or for a sacrifice.7If he takes a false sh'vuat hapikadon or sh'vuat ha'edut.

הלכה ב
אֶחָד הַנִּשְׁבָּע. אוֹ שֶׁהִשְׁבִּיעוֹ אַחֵר בַּשֵּׁם הַמְיֻחָד. אוֹ בְּאֶחָד מִן הַכִּנּוּיִין כְּגוֹן שֶׁנִּשְׁבַּע בְּמִי שֶׁשְּׁמוֹ חַנּוּן וּבְמִי שֶׁשְּׁמוֹ רַחוּם וּבְמִי שֶׁשְּׁמוֹ אֶרֶךְ אַפַּיִם. וְכַיּוֹצֵא בָּהֶן בְּכָל לָשׁוֹן הֲרֵי זוֹ שְׁבוּעָה גְּמוּרָה. וְכֵן אָלָה וְאָרוּר הֲרֵי הֵן שְׁבוּעָה. וְהוּא שֶׁיַּזְכִּיר שֵׁם מִן הַשֵּׁמוֹת אוֹ כִּנּוּי מִן הַכִּנּוּיִין. כֵּיצַד. כְּגוֹן שֶׁאָמַר בְּאָלָה אוֹ אָרוּר לַה'. אוֹ לְמִי שֶׁשְּׁמוֹ חַנּוּן. אוֹ לְמִי שֶׁשְּׁמוֹ רַחוּם. מִי שֶׁיֹּאכַל דָּבָר פְּלוֹנִי וַאֲכָלוֹ הֲרֵי זֶה נִשְׁבַּע לַשֶּׁקֶר. וְכֵן בִּשְׁאָר מִינֵי שְׁבוּעוֹת:
כסף משנה
2.
[The same laws apply whether] one took an oath - or another person administered an oath to him - with God's ineffable name8I.e., the name Yud-Hei-Vav-Hei. See Hilchot Avodat Kochavim 2:7 which states that this term also refers to the name Adonai. The same law holds true for any other of God's names. - or with one of the descriptive terms used to refer to Him,9Note, however, Hilchot Yesodei HaTorah 6:5, which states that even when these descriptions are used to refer to Him, they are not considered to have the same holiness as one of His names. e.g., he took an oath "on He whose name is Gracious," "on He whose name is Merciful," or "on He whose name is Patient," regardless of the language he used.10I.e., not only in lashon hakodesh, the Hebrew used in the Bible and by the Sages. The statement is considered an oath in the full sense of the term.11The Rambam uses the expression "in the full sense of the term" to differentiate between this instance and the law mentioned in Halachah 4. Note the Kessef Mishneh and the Radbaz who explains that there is a difference of opinion among the Rishonim if a sh'vuat bitui must contain God's name for one to be liable as appears to be the Rambam's opinion or whether His name need not be mentioned as is the view of the Ramban, Rabbenu Asher, and others. The Ra'avad takes an intermediate view, stating that one transgresses by taking a false oath and is liable to bring a sacrifice, but he is not liable for lashes unless he mentions one of God's names.
All authorities agree that God's name must be mentioned for one to be liable with regard to a sh'vuat haedut or a sh'vuat hapikadon. On that basis, the Radbaz supports the Rambam's position, asking why a differentiation should be made between one type of oath and another. See Shulchan Aruch (Yoreh De'ah 237:1) and commentaries.

Similarly, a statement with the terms eleh or erur12Both these terms mean "curse." is considered as an oath,13Sh'vuot 36a derives this concept from the verses cited above with regard to Tzidkayahu's oath, for there he used the term "curse." See also I Samuel 14, 24, 27 which indicate that saying that one will be cursed is equivalent to an oath. provided one mentions one of God's names or one of the terms used to describe Him. What is implied? When a person said: "May one who eats this-and-this entity be cursed unto God," or "...cursed unto He whose name is Gracious," "...cursed unto He whose name is Merciful" and then ate that entity, he has taken a false oath.14And is liable for taking a false sh'vuat bitui, as indicated by Chapter 1, Halachah 3. Similar concepts apply with regard to the other types of oaths.

הלכה ג
וְכֵן הָאוֹמֵר שְׁבוּעָה בַּה' אוֹ בְּמִי שֶׁשְּׁמוֹ חַנּוּן שֶׁלֹּא אֹכַל וְאָכַל. שֶׁזּוֹ אִשָּׁה וְהוּא אִישׁ. שֶׁאֵין לְךָ בְּיָדִי כְּלוּם וְיֵשׁ לוֹ. שֶׁאֵינִי יוֹדֵעַ לְךָ עֵדוּת וְהוּא יוֹדֵעַ. הֲרֵי זֶה חַיָּב:
כסף משנה
3.
Similarly, one who says: "[I am taking] an oath by God...," or "...by One whose name is Gracious that I will not eat," and he ate, "...that this is a woman," and it was a man, "...that I do not owe you anything," and he does, "that I do not know any testimony involving you," and he does,15I.e., the Rambam is giving an example of all four types of oaths. he is liable.

הלכה ד
אָמַר אָלָה אוֹ אָרוּר אוֹ שְׁבוּעָה וְלֹא הִזְכִּיר שֵׁם וְלֹא כִּנּוּי הֲרֵי זֶה אָסוּר בַּדָּבָר שֶׁנִּשְׁבַּע עָלָיו. אֲבָל אֵינוֹ לוֹקֶה וְלֹא מֵבִיא קָרְבָּן אִם עָבַר עַל שְׁבוּעָתוֹ עַד שֶׁיִּהְיֶה בָּהּ שֵׁם מִן הַשֵּׁמוֹת הַמְּיֻחָדִים אוֹ כִּנּוּי מִן הַכִּנּוּיִין כְּמוֹ שֶׁבֵּאַרְנוּ:
כסף משנה
4.
If a person uses the term eleh or erur or an oath and does not mention God's name or a term describing Him, he is bound by a prohibition with regard to the entity concerning which he [desired to] take the oath. He is not, however, liable for lashes or for a sacrifice if he violated his oath unless it included one of God's names16See Hilchot Yesodei HaTorah 6:2 for a list of the seven names of God. or a term describing Him as explained.

הלכה ה
וְלֹא הַשְּׁבוּעָה בִּלְבַד אֶלָּא כָּל כִּנּוּיֵי שְׁבוּעָה כִּשְׁבוּעָה. כְּגוֹן שֶׁהָיוּ אַנְשֵׁי אוֹתוֹ מָקוֹם עִלְּגִים וְהָיוּ קוֹרְאִים לִשְׁבוּעָה שְׁבוּתָהּ אוֹ שְׁקוּקָה. אוֹ שֶׁהָיוּ אֲרַמִּיִּים שֶׁלְּשׁוֹן שְׁבוּעָה בִּלְשׁוֹנָם מוֹמְתָא. וְהָעִלְּגִים מְכַנִּין אוֹתָהּ וְאוֹמְרִים מוֹהָא. כֵּיוָן שֶׁאָמַר לָשׁוֹן שֶׁמַּשְׁמָעוֹ וְעִנְיָנוֹ שְׁבוּעָה הֲרֵי זֶה חַיָּב כְּמִי שֶׁהוֹצִיא לְשׁוֹן שְׁבוּעָה:
כסף משנה
5.
Not only the term sh'vuah, but [the use of] any idiom used to refer to an oath is considered as [taking] an oath. For example, people in a given place were inarticulate and would call an oath shabutah or shakukah, or they were Aramites for whom the term for oath in their language is momata, and the inarticulate idiomatically refer to it is mohah. When a person makes a statement whose intent and meaning is that he is taking an oath, he is liable as if he used the term [in Lashon Hakodesh].17For that reason, when called to take an oath in a secular court or the like, one should refuse. Instead of saying "I swear," he should say, "I affirm."

הלכה ו
וְכֵן הָאוֹמֵר לָאו לָאו שְׁתֵּי פְּעָמִים דֶּרֶךְ שְׁבוּעָה אוֹ הֵן הֵן וְהִזְכִּיר שֵׁם אוֹ כִּנּוּי הֲרֵי זֶה כְּנִשְׁבָּע. וְכֵן יָמִין שְׁבוּעָה. וּשְׂמֹאל שְׁבוּעָה. שֶׁנֶּאֱמַר (ישעיה סב ח) "נִשְׁבַּע ה' בִּימִינוֹ וּבִזְרוֹעַ עֻזּוֹ". וְכֵן הָאוֹמֵר מִבְטָא שֶׁלֹּא אֶעֱשֶׂה כָּךְ וְכָךְ וְהִזְכִּיר שֵׁם אוֹ כִּנּוּי הֲרֵי זוֹ שְׁבוּעָה:
כסף משנה
6.
Similarly, when a person says: "No, no," repeating the negative twice as if he is taking an oath or "Yes, yes," and mentions God's name or a term used to describe Him, it is considered an oath.18The repetition and the mention of God's name indicate that he is not merely making a statement, but intending that it have the severity of an oath. The Kessef Mishneh states that since the person mentioned God's name, seemingly, it is not necessary for him to repeat yes or no, the mention of His name alone should be sufficient for his statement to be considered an oath. He explains that we are speaking about an instance when God's name was not mentioned in direct connection with the statement. Nevertheless, the fact that he repeated no, or yes while mentioning God's name, albeit indirectly, is sufficient for his statements to be considered an oath. Similarly, if he says: "[By God's] right hand," it is an oath, or "[By God's] left hand," it is an oath, as [implied by Isaiah 62:5] "God swore by His right hand and by the arm of His strength."192Nazir 3a states that "the arm of His strength" refers to His left arm. Otherwise, the verse would be redundant. Similarly, when someone says "Mivtah20Sh'vuot 20a notes that Numbers 30:7 understands this term as referring to an oath. that I will not do such-and-such," and mentions God's name or a term used to describe Him, it is considered an oath.

הלכה ז
אָמַר אִסָּר לַה' אוֹ לְמִי שֶׁשְּׁמוֹ חַנּוּן שֶׁאֶעֱשֶׂה אוֹ שֶׁלֹּא אֶעֱשֶׂה הוֹאִיל וְהוֹצִיאוֹ בִּלְשׁוֹן שְׁבוּעָה הֲרֵי הִיא כִּשְׁבוּעָה:
כסף משנה
7.
When one says: "It is forbidden for God's [sake]" or "...for [the sake of] He whose name is Gracious that I will do..." or "...that I will not do [such-and-such]," it is considered an oath, because the wording he used has that implication.

הלכה ח
שָׁמַע חֲבֵרוֹ נִשְׁבָּע וְאָמַר וַאֲנִי כְּמוֹתְךָ הוֹאִיל וְלֹא הוֹצִיא שְׁבוּעָה מִפִּיו וְלֹא הִשְׁבִּיעוֹ חֲבֵרוֹ הֲרֵי זֶה פָּטוּר. וְזֶהוּ מַתְפִּיס בִּשְׁבוּעָה שֶׁהוּא פָּטוּר:
כסף משנה
8.
If he heard his colleague take an oath and said: "I am like him," he is not liable,21In his Kessef Mishneh, Rav Yosef Caro states that the Rambam's choice of wording - "He is not liable" rather than "It is permitted" - implies that although he is not liable, he is forbidden to break the commitment he made. Although other Rishonim differ, he follows this interpretation in his Shulchan Aruch (Yoreh De'ah 239:9-10). See the following halachah. for he did not utter an oath, nor did his colleague administer an oath to him. This is "appending" to an oath for which one is not liable.22This is one of the distinctions between oaths and vows. One who "appends" - i.e., says "And I will be like him" - to a colleague's vow is liable. See Hilchot Nedarim 3:3-4.

הלכה ט
וְכֵן אִם נִשְׁבַּע שֶׁלֹּא אֹכַל בָּשָׂר זֶה. וְחָזַר וְאָמַר וַהֲרֵי הַפַּת זוֹ כַּבָּשָׂר הַזֶּה הֲרֵי הוּא פָּטוּר עַל הַפַּת. שֶׁהֲרֵי לֹא הוֹצִיא שְׁבוּעָה מִפִּיו עָלֶיהָ אֶלָּא הִתְפִּיסָהּ. וְאַף עַל פִּי שֶׁהוּא פָּטוּר מִן הַמַּלְקוֹת אוֹ מִן הַקָּרְבָּן אָסוּר לוֹ לֶאֱכל אוֹתָהּ הַפַּת שֶׁהִתְפִּיס בִּשְׁבוּעָה:
כסף משנה
9.
Similarly, if he took an oath and said: "I will not eat this meat," and then said: "This bread is like this meat," he is not liable for the bread, because he did not explicitly take an oath regarding it. Instead, he appended [the prohibition concerning it to his existing oath]. Although he is exempt from lashes and from a sacrifice, he is forbidden to partake of the bread that he appended to his oath.23The Radbaz explains that the Rambam elaborates here - in contrast to the previous halachah - for here there is greater reason to think that he will not be obligated. The explanation is based on a fundamental understanding of the difference between a sh'vuah - oath - and a neder - vow. When a person takes an oath, he places a prohibition upon his person - he is forbidden to perform the activity concerning which he took the oath. When he takes a vow, the article becomes forbidden for him. Hence, since he spoke about the article and not himself, one might think that his statement has no effect at all.

הלכה י
מִי שֶׁנִּתְכַּוֵּן לִשְׁבוּעָה וְגָמַר בְּלִבּוֹ שֶׁלֹּא יֹאכַל הַיּוֹם אוֹ שֶׁלֹּא יִשְׁתֶּה וְשֶׁדָּבָר זֶה אָסוּר עָלָיו בִּשְׁבוּעָה וְלֹא הוֹצִיא בִשְׂפָתָיו הֲרֵי זֶה מֻתָּר שֶׁנֶּאֱמַר (ויקרא ה ד) "לְבַטֵּא בִּשְׂפָתַיִם". אֵין הַנִּשְׁבָּע חַיָּב עַד שֶׁיּוֹצִיא עִנְיַן שְׁבוּעָה בִּשְׂפָתָיו:
כסף משנה
10.
[Although] a person has the intent to take an oath and resolves in his heart not to eat on that day or not to drink and has the intent for that activity to be forbidden for him by oath, [if] he does not actually make such a statement, he is permitted [to eat or drink], as [implied by Leviticus 5:4]: "expressing with his lips." [Implied is that] a person who takes an oath is not liable until he explicitly states the matter the oath concerns with his lips.

הלכה יא
וְכֵן אִם גָּמַר בְּלִבּוֹ לְהִשָּׁבַע וְטָעָה וְהוֹצִיא בִּשְׂפָתָיו דָּבָר שֶׁלֹּא הָיָה בְּלִבּוֹ הֲרֵי זֶה מֻתָּר. כֵּיצַד. הַמִּתְכַּוִּן לְהִשָּׁבַע שֶׁלֹּא יֹאכַל אֵצֶל רְאוּבֵן וּכְשֶׁבָּא לְהוֹצִיא שְׁבוּעָה נִשְׁבַּע שֶׁלֹּא יֹאכַל אֵצֶל שִׁמְעוֹן. הֲרֵי זֶה מֻתָּר לֶאֱכל עִם רְאוּבֵן שֶׁהֲרֵי לֹא הוֹצִיאוֹ בִּשְׂפָתָיו. וְעִם שִׁמְעוֹן שֶׁהֲרֵי לֹא הָיָה שִׁמְעוֹן בְּלִבּוֹ:
כסף משנה
11.
Similarly, if he resolved within his heart to take an oath and erred and uttered a statement that did not fit the intent in his heart, [the activity] is permitted.24For as Sh'vuot 26b implies, one's heart and one's lips must be in concord.
What is implied? A person had the intent that he would not eat in Reuven's [home], but when he actually came to state the oath explicitly, he swore not to eat in [Shimon's] home. [In such a situation,] he is permitted to eat in Reuven's [home] for he did not explicitly [swear not to eat there]. [And he is permitted to eat] in Shimon's [home] for he did not have the intent [to prohibit that].

הלכה יב
וְכֵן שְׁאָר מִינֵי שְׁבוּעוֹת אֵינוֹ חַיָּב עַד שֶׁיִּהְיֶה פִּיו וְלִבּוֹ שָׁוִין. לְפִיכָךְ אִם נִשְׁבַּע אֶחָד בְּפָנֵינוּ שֶׁלֹּא יֹאכַל הַיּוֹם וְאָכַל. וְהִתְרוּ בּוֹ וְאָמַר אֲנִי לֹא הָיָה בְּלִבִּי אֶלָּא שֶׁלֹּא אֵצֵא הַיּוֹם וְטָעָה לְשׁוֹנִי וְהוֹצִיא אֲכִילָה שֶׁלֹּא הָיְתָה בְּלִבִּי הֲרֵי זֶה אֵינוֹ לוֹקֶה. עַד שֶׁיּוֹדֶה בִּפְנֵי עֵדִים קֹדֶם שֶׁיֹּאכַל שֶׁעַל אֲכִילָה נִשְׁבַּע. אוֹ שֶׁקִּבֵּל עָלָיו הַתְרָאָה וְלֹא טָעַן שֶׁטָּעָה בְּעֵת הַתְרָאָה אַף עַל פִּי שֶׁטָּעַן אַחַר כָּךְ אֵין שׁוֹמְעִין לוֹ. וְכֵן אִם הִתְרוּ בּוֹ וְאָמַר מֵעוֹלָם לֹא נִשְׁבַּעְתִּי אוֹ לֹא נָדַרְתִּי אֶלָּא עַל דָּבָר זֶה וְאַחַר שֶׁהֵעִידוּ עָלָיו שֶׁנִּשְׁבַּע אוֹ נָדַר אָמַר כֵּן הָיָה אֲבָל לֹא הָיָה פִּי וְלִבִּי שָׁוִין אוֹ תְּנַאי הָיָה בְּלִבִּי עַל הַנֵּדֶר אֵין שׁוֹמְעִין לוֹ וְלוֹקֶה:
כסף משנה
12.
Similarly, with regard to the other types of oaths, one is not liable until his mouth and his heart are in concord.25In some authoritative manuscripts and early printings of the Mishneh Torah, this sentence is the conclusion of the previous halachah. The present halachah begins: "Therefore..." Compare to Halachot 15-16. Therefore [the following law applies if] a person took an oath in our presence that he would not eat and ate. He was given a warning [before he ate] and he responded: "My intent was that I would not depart today. I had a slip of the tongue and mentioned eating although that was not my intent."26I.e., if he makes this statement when given the warning, we accept his word and do not hold him liable (Tosefta, Taharot 6:9). is not liable for lashes unless, before he eats, he admits in the presence of witnesses that [his intent in] taking the oath was [not] to eat. Alternatively, [he is liable for lashes] if he accepted the warning and did not protest that he erred at the time of the warning. Even though he protested afterwards, we do not pay attention to him.27As stated in Hilchot Sanhedrin 12:2, to be liable for lashes, a transgressor must acknowledge the warning. Since, at that time, he did not mention the lack of concurrence between his intent and his statements, we assume that he is fabricating the matter. Similarly, [he is liable] if they warned him and he said: "I never took an oath - or a vow - concerning this matter." Despite the fact that after they give testimony that he took an oath or vow, he says: "Yes, that is true, but my mouth and heart were not in concord," or "In my heart, I had a stipulation in mind concerning the vow,"28And since the stipulation was not met, the vow is not binding. we do not heed him29For he has already lied concerning this oath. and he is liable for lashes.

הלכה יג
כַּיּוֹצֵא בּוֹ אָמְרוּ לוֹ אִשְׁתְּךָ נָדְרָה. וְאָמַר בְּלִבִּי הָיָה לְהָפֵר לָהּ וְהֵפַרְתִּי שׁוֹמְעִין לוֹ. אָמְרוּ לוֹ נָדְרָה וְהוּא אוֹמֵר לֹא נָדְרָה וְכֵיוָן שֶׁרָאָה אוֹתָם הֵעִידוּ עָלָיו אָמַר בְּלִבִּי הָיָה לְהָפֵר אֵין שׁוֹמְעִין לוֹ:
כסף משנה
13.
Similarly, if [witnesses] told him: "Your wife took a vow," and he said: "My intent was to nullify the vow and I did so,"30There is a difference of opinion among the commentaries with regard to the interpretation of the Rambam's statements. Some explain that the intent is that the husband used the halachic convention of hafarah and made the statement nullifying his wife's vow in a hushed tone. If, however, he did not make a statement of hafarah at all, the vow is not nullified, as stated in Hilchot Nedarim 13:7). The Tzaphnat Paneach states that the intent is that he used the halachic convention of bittul. In such in instance, a statement need not be made (Hilchot Nedarim 13:4). we heed his statements. If he is told, "She took a vow," and he denies it, but when he saw them testify against him, he said: "My intent was to nullify [the vow]," his word is not heeded.

הלכה יד
גָּמַר בְּלִבּוֹ שֶׁלֹּא לֶאֱכל פַּת חִטִּין וְנִשְׁבַּע שֶׁלֹּא יֹאכַל פַּת סְתָם אָסוּר בְּפַת חִטִּים שֶׁפַּת חִטִּים פַּת שְׁמָהּ:
כסף משנה
14.
If he resolved within his heart not to partake of bread made from wheat, but took an oath not to partake of bread without qualifying his statement, he is forbidden to partake of bread from wheat. For when bread [is mentioned without qualification, the meaning] is bread from wheat.31Thus the person cannot claim that his statement did not reflect his intent.

הלכה טו
מִי שֶׁנִּשְׁבַּע וְאָמַר שְׁבוּעָה שֶׁלֹּא אֹכַל הַיּוֹם וְעַל דַּעְתְּכֶם אֲנִי נִשְׁבָּע. אֵין זֶה יָכוֹל לוֹמַר כָּךְ וְכָךְ הָיָה בְּלִבִּי. שֶׁלֹּא נִשְׁבַּע זֶה עַל דַּעְתּוֹ אֶלָּא עַל דַּעַת אֲחֵרִים וְכֵיוָן שֶׁהָיָה פִּיו וְלִבָּם שֶׁל אֲחֵרִים שֶׁנִּשְׁבַּע עַל דַּעְתָּם שָׁוִים חַיָּב מִפְּנֵי שֶׁלִּבָּם שֶׁל אֵלּוּ בִּמְקוֹם לִבּוֹ קָם. וְכֵן בִּשְׁאָר מִינֵי שְׁבוּעוֹת:
כסף משנה
15.
When a person takes an oath, saying: "[I am taking] an oath that I will not eat today and my oath is dependent on your intent,"32I.e., this law applies even if the person takes the oath on his own volition, not only if it is administered by others. he cannot [later] say: "I had these-and-these thoughts in my heart." [The rationale is] that the person did not take the oath dependent on his own intent, but rather on the intent of others. Since his statements did concur with the intent of those on whose intent he took the oath he is liable. [The intent in] the heart of those individuals takes the place of his own intent. [This concept also applies] with regard to other types of oaths.

הלכה טז
לְפִיכָךְ כְּשֶׁמַּשְׁבִּיעִין הַדַּיָּנִין אֶת הַנִּשְׁבָּע אוֹמְרִים לוֹ לֹא עַל דַּעְתְּךָ אָנוּ מַשְׁבִּיעִים אוֹתְךָ אֶלָּא עַל דַּעְתֵּנוּ:
כסף משנה
16.
Therefore when judges administer an oath to a person,33I.e., require an oath of a person who denies a plaintiff's claim. See Chapter 11, Halachah 18. they tell him: "We are not administering the oath dependent on your intent, but dependent on our intent.34Thus afterwards the person cannot claim that he had these-and-these thoughts in mind when taking the oath (Radbaz). See also Nedarim 25a.

הלכה יז
מִי שֶׁנִּשְׁבַּע וְהָיָה פִּיו וְלִבּוֹ שָׁוִין בִּשְׁבוּעָה. וְאַחַר שֶׁנֶּאֱסַר חָזַר בּוֹ מִיָּד בְּתוֹךְ כְּדֵי דִּבּוּר וְהוּא כְּדֵי שֶּׁיֹּאמַר תַּלְמִיד לְרַב שָׁלוֹם עָלֶיךָ רַבִּי. וְאָמַר אֵין זוֹ שְׁבוּעָה אוֹ נִחַמְתִּי אוֹ חָזַרְתִּי בִּי וְכַיּוֹצֵא בִּדְבָרִים אֵלּוּ שֶׁעִנְיָנָם שֶׁהִתִּיר מַה שֶּׁאָסַר הֲרֵי זֶה מֻתָּר וְנֶעֶקְרָה הַשְּׁבוּעָה שֶׁזֶּה דּוֹמֶה לְטוֹעֶה:
כסף משנה
17.
[The following law applies when a person] took an oath and his statements and his intent concurred at the time he took the oath, but after he becomes forbidden [in the particular activity mentioned in the oath], he changes his mind immediately, directly after he spoke. [The latter term has a specific halachic definition]: the time it takes a student to tell his teacher: Shalom Elecha Rabbi.35"Greetings to you, my teacher." We have cited the term in transliteration for we are speaking about the amount of time it takes to say these three Hebrew words. [If, in this interim, the person says:] "This is not an oath," "I changed my mind," "I retract," or the like, i.e., statements that imply that he seeks to release the prohibition he took on [himself], it is permitted.36Nedarim 87a states that this principle applies with the exception of four situations: a blasphemer, one who accepts a false deity, one who consecrates a woman as a wife, and one who divorces her. Rabbenu Nissim explains that when taking an oath, a person has in mind that he might change his mind in this brief amount of time. Hence, his oath is not binding until this time passes. The oath is eradicated, for this resembles one who made a statement in error.

הלכה יח
וְכֵן אִם אָמְרוּ לוֹ אֲחֵרִים חֲזֹר בְּךָ אוֹ מֻתָּר לְךָ וְכַיּוֹצֵא בִּדְבָרִים אֵלּוּ וְקִבֵּל מֵהֶן בְּתוֹךְ כְּדֵי דִּבּוּר וְאָמַר הֵן אוֹ חָזַרְתִּי בִּי וְכַיּוֹצֵא בָּזֶה הֲרֵי זֶה מֻתָּר. וְאִם אַחַר כְּדֵי דִּבּוּר אֵינוֹ יָכוֹל לַחְזֹר בּוֹ:
כסף משנה
18.
Similarly, if others tell him: "Retract," "It is permitted for you," or the like and he accepts their view within the above measure of time37The Ra'avad objects to the Rambam's ruling, saying that the objections of others cannot by connected to his oath. In his Kessef Mishneh and in his Shulchan Aruch (Yoreh De'ah 210:3), Rav Yosef Caro and also the Radbaz explain that since the others protested immediately after his oath and his acceptance also came immediately afterwards, it is as if he never completed taking the oath. by saying: "Yes," or "I retract," he is permitted. After this measure of time, he cannot retract.38This applies even if the oath has not taken effect as of yet (Radbaz).

הלכה יט
נִשְׁבַּע וְחָזַר בּוֹ בְּתוֹךְ כְּדֵי דִּבּוּר בְּלִבּוֹ אֵין זֶה כְּלוּם. וְכֵן אִם אָמְרוּ לוֹ אֲחֵרִים חֲזֹר בְּךָ אוֹ מֻתָּר לְךָ אוֹ מָחוּל לְךָ וְקִבֵּל דִּבְרֵיהֶם בְּלִבּוֹ בְּתוֹךְ כְּדֵי דִּבּוּר אֵין זֶה כְּלוּם עַד שֶׁיּוֹצִיא הַחֲזָרָה בְּפִיו כְּמוֹ הַשְּׁבוּעָה:
כסף משנה
19.
If a person took an oath and retracted within his heart39I.e., without verbalizing his retraction. within the above measure of time, it is of no consequence. Similarly, if others told him: "Retract," "It is permitted for you," or "It is absolved for you," and he accepted their words in his heart within the above measure of time, it is of no consequence. He must state his retraction explicitly like his oath.40The Radbaz emphasizes that he must also make his statements with intent. Just as his mouth and heart must concur when making an oath, so, too, they must concur when retracting it.

הפלאה הלכות שבועות פרק ב
Haflaah Shevuos Chapter 2