Halacha

הלכה א
כָּל הַנִּשְׁבָּע שְׁבוּעָה מֵאַרְבַּע מִינֵי שְׁבוּעוֹת אֵלּוּ בְּאֹנֶס הֲרֵי זֶה פָּטוּר מִכְּלוּם. וְאֶחָד הַנִּשְׁבָּע מִתְּחִלָּתוֹ בְּאֹנֶס כְּמוֹ שֶׁבֵּאַרְנוּ. אוֹ שֶׁנִּשְׁבַּע וְנֶאֱנַס וְלֹא הִנִּיחוּהוּ לְקַיֵּם שְׁבוּעָתוֹ. אוֹ שֶׁהִשְׁבִּיעוֹ אַנָּס. לְפִיכָךְ נִשְׁבָּעִין לַחֲרָמִין וּלְהוֹרְגִין וּלְמוֹכְסִין:
כסף משנה
1.
Whenever a person takes one of these four types of oaths under compulsion, he is exempt from all liability. This applies to a person who at the outset took a false oath because of factors beyond his control as we explained, one who took an oath and then was subjected to compulsion and was not given the opportunity to fulfill his oath, or he was compelled to take an oath by a man of force. Therefore one may take an oath when compelled to by robbers, potential murders, and tax collectors.

הלכה ב
בְּאֵי זֶה מוֹכֵס אָמְרוּ. בְּמוֹכֵס הָעוֹמֵד מֵאֵלָיו שֶׁלּוֹקֵחַ מָמוֹן שֶׁלֹּא בִּרְשׁוּת מֶלֶךְ הַמְּדִינָה. אוֹ שֶׁלּוֹקֵחַ בִּרְשׁוּת הַמֶּלֶךְ אֲבָל מוֹסִיף לְעַצְמוֹ עַל הַדָּבָר הַקָּצוּב כְּמוֹ שֶׁיִּתְבָּאֵר בְּהִלְכוֹת גְּזֵלָה:
כסף משנה
2.
To which tax collector did we refer? To a tax collector that assumed the position on his own, who takes money without the license of the king or who takes money with the king's license, but takes more for himself than the fixed measure, as explained in Hilchot Gezelah.

הלכה ג
וְצָרִיךְ הַנִּשְׁבָּע בְּאֹנֶס לִהְיוֹת כַּוָּנָתוֹ בְּלִבּוֹ בְּעֵת הַשְּׁבוּעָה לְדָבָר הַפּוֹטְרוֹ. וְאַף עַל פִּי שֶׁהַדְּבָרִים אֵלּוּ שֶׁבַּלֵּב אֵינָן דְּבָרִים. הוֹאִיל וְאֵינוֹ יָכוֹל לְהוֹצִיא בִּשְׂפָתָיו מִפְּנֵי הָאֹנֶס. הֲרֵי זֶה סוֹמֵךְ עַל דְּבָרִים שֶׁבְּלִבּוֹ:
כסף משנה
3.
When a person is compelled to take an oath, to be exempt, while taking the oath, he must have the intent in his heart for the oath to apply to something for which he is exempt. Although generally, words in a person's heart are of no consequence, since he cannot express his intent because of the forces beyond his control, he can rely on the intent in his heart.

הלכה ד
כֵּיצַד. כְּגוֹן שֶׁנִּשְׁבַּע לְאַנָּס שֶׁלֹּא יֹאכַל בָּשָׂר סְתָם. וּבְלִבּוֹ שֶׁלֹּא יֹאכַל הַיּוֹם אוֹ שֶׁלֹּא יֹאכַל בְּשַׂר חֲזִיר הֲרֵי זֶה מֻתָּר. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה:
כסף משנה
4.
What is implied? One took an oath to a man of force that he would not eat meat without qualifying his statement, it is permitted if in his heart, he had the intent that he was saying that he would not eat the meat of pigs, or that he would not eat meat that day. Similar laws apply in all analogous situations.

הלכה ה
וְכֵן שְׁבוּעַת הֲבַאי וְשֶׁל שְׁגָגוֹת פָּטוּר עֲלֵיהֶן. שְׁבוּעַת (שֶׁל) הֲבַאי כֵּיצַד. כְּגוֹן שֶׁרָאָה חֵילוֹת גְּדוֹלוֹת וְחוֹמָה גְּבוֹהָה וְנִשְׁבַּע שֶׁרָאִיתִי חֵיל פְּלוֹנִי הַמֶּלֶךְ וְהֵם כְּיוֹצְאֵי מִצְרַיִם. וְשֶׁרָאִיתִי חוֹמַת עִיר פְּלוֹנִית גְּבוֹהָה עַד לָרָקִיעַ וְכַיּוֹצֵא בִּדְבָרִים אֵלּוּ. שֶׁזֶּה לֹא גָּמַר בְּלִבּוֹ שֶׁהַדָּבָר כָּךְ בְּלֹא פָּחוֹת וְלֹא יוֹתֵר וְלֹא נִתְכַּוֵּן אֶלָּא לְסַפֵּר אֶת גֹּבַהּ הַחוֹמָה אוֹ רֹב הָעָם:
כסף משנה
5.
Similarly, one is not liable for oaths involving exaggerations or unintentional oaths. What is meant by oaths involving exaggerations? A person saw vast armies and tall walls and he took an oath that "I saw the armies of King So-and-So and they are as vast as those who left Egypt," "I saw the wall of this-and-this city and it was as high as the heavens," or the like. He is exempt, because he did not resolve within his heart that this was the measure of the subject in question, no more and no less. His intent was only to describe the height of the wall or the multitude of the people.

הלכה ו
שְׁבוּעָה שֶׁל שְׁגָגוֹת כֵּיצַד. אִם שְׁבוּעַת הָעֵדוּת אוֹ הַפִּקָּדוֹן הִיא כְּגוֹן שֶׁשָּׁגַג בְּפִקָּדוֹן וּבְעֵדוּת שֶׁהוּא פָּטוּר מִכְּלוּם כְּמוֹ שֶּׁבֵּאַרְנוּ. וְאִם שְׁבוּעַת שָׁוְא הִיא כְּגוֹן שֶׁנִּשְׁבַּע שֶׁלֹּא יִלְבַּשׁ תְּפִלִּין וְלֹא יָדַע שֶׁהַתְּפִלִּין מִצְוָה. וְאִם שְׁבוּעַת שֶׁקֶר הִיא כְּגוֹן שֶׁנִּשְׁבַּע שֶׁלֹּא אָכַל וְנִזְכַּר שֶׁאָכַל. אוֹ שֶׁנִּשְׁבַּע שֶׁלֹּא יֹאכַל וְשָׁכַח וְאָכַל. אוֹ שֶׁלֹּא תֵּהָנֶה אִשְׁתּוֹ לוֹ מִפְּנֵי שֶׁגָּנְבָה כִּיסוֹ אוֹ שֶׁהִכְּתָה אֶת בְּנוֹ וְנוֹדַע שֶׁלֹּא גָּנְבָה וְשֶׁלֹּא הִכְּתָה. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה:
כסף משנה
6.
What is meant by an oath taken inadvertently? With regard to a sh'vuat hapikadon or a sh'vuat ha'edut, it refers to a situation where the person forgot about the entrusted article or the testimony. He is entirely exempt, as we explained.
With regard to an oath taken in vain, it refers to a situation where the person took an oath not to wear tefilin, but did not know that tefilin are a mitzvah. With regard to a false oath, it refers to a situation where the person took an oath that he did not eat and then remembered that he did in fact eat, he took an oath that he would not eat and then forgot and ate, he took an oath that he would not give any satisfaction to his wife because she stole his wallet or beat his son and afterwards, he found out that she did not steal it or beat him. Similar concepts apply in all analogous situations.

הלכה ז
אִם כֵּן אֵי זֶהוּ שִׁגְגַת שְׁבוּעַת בִּטּוּי שֶׁחַיָּבִין עָלֶיהָ קָרְבַּן עוֹלֶה וְיוֹרֵד לְשֶׁעָבַר. כְּגוֹן שֶׁנִּשְׁבַּע שֶׁלֹּא אָכַל וְהוּא יוֹדֵעַ שֶׁאָכַל. וְשֶׁשְּׁבוּעַת שֶׁקֶר זוֹ שֶׁנִּשְׁבַּע אֲסוּרָה אֲבָל לֹא יָדַע שֶׁחַיָּבִין עָלֶיהָ קָרְבָּן. זוֹ הִיא הַשְּׁגָגָה שֶׁחַיָּבִין עָלֶיהָ קָרְבַּן עוֹלֶה וְיוֹרֵד בִּשְׁבוּעַת בִּטּוּי לְשֶׁעָבַר:
כסף משנה
7.
If so, what is a sh'vuat bitui taken inadvertently for which one is liable to bring an adjustable guilt offering with regard to the past? One took an oath that he did not eat although he knew that he in fact had eaten and he knew that it is forbidden to have taken this false oath, but he did not know that he is liable to bring a sacrifice for it. This is the inadvertent violation for which one is liable to bring an adjustable guilt offering for taking a sh'vuat bitui with regard to the past.

הלכה ח
וְכֵיצַד הִיא הַשְּׁגָגָה שֶׁחַיָּבִין עָלֶיהָ קָרְבָּן לְהַבָּא. כְּגוֹן שֶׁנִּשְׁבַּע שֶׁלֹּא יֹאכַל פַּת חִטִּים וְשָׁגַג וְדִמָּה שֶׁנִּשְׁבַּע שֶׁיֹּאכַל פַּת חִטִּים וַאֲכָלָהּ שֶׁזֶּה נֶעֶלְמָה מִמֶּנּוּ הַשְּׁבוּעָה הֵיאַךְ הָיְתָה וַהֲרֵי הוּא זוֹכֵר אֶת הַחֵפֶץ שֶׁנִּשְׁבַּע עָלָיו. זוֹ הִיא שִׁגְגַת שְׁבוּעַת בִּטּוּי לְהַבָּא שֶׁחַיָּבִין עָלֶיהָ קָרְבָּן:
כסף משנה
8.
What is meant by an inadvertent violation for which one is liable for an adjustable guilt offering for breaking an oath involving the future? For example, one took an oath that he would not eat bread from wheat and forgot and thought that he had taken an oath that he would eat bread from wheat and then ate it. In this instance, he became unaware of the content of the oath although he remembered the article concerning which he took the oath. This is an inadvertent violation of a sh'vuat bitui involving the future which obligates him to bring a sacrifice.

הלכה ט
אֲבָל אִם נִשְׁבַּע שֶׁלֹּא יֹאכַל פַּת חִטִּים וְאָכַל פַּת חִטִּים עַל דַּעַת שֶׁהוּא פַּת שְׂעוֹרִים הֲרֵי זֶה אָנוּס וּפָטוּר. שֶׁהֲרֵי לֹא נֶעֶלְמָה מִמֶּנּוּ שְׁבוּעָה וְלֹא נֶעְלָם מִמֶּנּוּ אֶלָּא חֵפֶץ שֶׁנִּשְׁבַּע עָלָיו:
כסף משנה
9.
If, however, he took an oath that he would not eat bread from wheat and he ate bread from wheat thinking that it was made from barley, he is considered to have transgressed due to forces beyond his control and he is exempt. For he did not become unaware of the oath, but instead of the article concerning which he took the oath.

הלכה י
נֶעֶלְמָה מִמֶּנּוּ שְׁבוּעָה הֵיאַךְ הָיְתָה וְנֶעְלַם מִמֶּנּוּ חֵפֶץ שֶׁנִּשְׁבַּע עָלָיו הֲרֵי זֶה פָּטוּר מִן הַקָּרְבָּן. כֵּיצַד. כְּגוֹן שֶׁנִּשְׁבַּע שֶׁלֹּא לֶאֱכל פַּת חִטִּים וְדִמָּה שֶׁנִּשְׁבַּע שֶׁיֹּאכַל פַּת חִטִּים וְאָכַל פַּת חִטִּים עַל דַּעַת שֶׁהוּא פַּת שְׂעוֹרִים שֶׁהֲרֵי הֶעְלֵם שְׁבוּעָה וְחֵפֶץ בְּיָדוֹ הֲרֵי זֶה כְּאָנוּס וּפָטוּר:
כסף משנה
10.
If he lost awareness of the oath he took and he lost awareness of the article concerning which he took the oath, he is not liable for a sacrifice.
What is implied? For example, one took an oath that he would not eat bread from wheat and thought that he had taken an oath that he would eat bread from wheat and ate bread from wheat thinking it was barley. He is not liable, because he became unaware of both the oath and the article it concerned. It is considered as if he he transgressed due to forces beyond his control.

הלכה יא
נִשְׁבַּע עַל כִּכָּר שֶׁלֹּא יֹאכְלֶנּוּ וְנִצְטַעֵר עָלָיו וַאֲכָלוֹ מִפְּנֵי הַצַּעַר וְהוּא שׁוֹגֵג שֶׁהֲרֵי דִּמָּה שֶׁמֻּתָּר לוֹ לְאָכְלוֹ מִפְּנֵי הַצַּעַר הֲרֵי זֶה פָּטוּר מִן הַקָּרְבָּן לְפִי שֶׁאֵינוֹ שָׁב מִידִיעָתוֹ אֶלָּא יָדַע שֶׁאֲסוּרָה הִיא וַאֲכָלָהּ בְּטָעוּת:
כסף משנה
11.
The following laws apply if a person took an oath concerning a loaf of bread, swearing that he would not eat it and then suffered discomfort because of it. Should he eat the loaf because of his discomfort, because he thought that it is permitted for him to eat it because of discomfort, he is considered to have transgressed inadvertently. He is exempt from bringing a sacrifice, because he is not repenting because of his new knowledge. Instead, he knew that it was forbidden and ate it in error.

הפלאה הלכות שבועות פרק ג
Haflaah Shevuos Chapter 3