Halakhah su Levitico 5:4

However, we were not permitted to go out from it [wantonly, but] rather [only] with the stratagem and counsel of the sage; that the one who swore come in front of the man who is wise and understanding of the ways of the Torah and confess to him that [the oath] was from his lack of knowledge - that he did not know at the time that he swore something that he knew afterwards - that he wants to annul what he swore about (Nedarim 71a); and that he recognizes that the smallness of his knowledge and his lacking caused the annulment, not something else or an external thought that would be in his heart, God forbid. And after the confession of his mouth about this, the sage recognizes and sees that there is substance in his words that something new happened to him that if he had had to agree to it at the time that he swore, he would not have sworn and that this is why he regrets [it]; he accepts his confession and he releases him from his oath. And this is what they, may their memory be blessed, said (Berachot 32b), "He cannot forgive [it], but others can forgive it to him." Therefore it is never possible to annul an oath, except with the reason of something new to the one who swore - for example, that he will say, "If I had known thing x, I would never have sworn." As this is like duress. But if he says, "Annul me my oath," without a claim, no man has the power to annul it. And based on this, they, may their memory be blessed, said (Nedarim 64a) that we do not create an opening (to annul the vow) with something new that is not found (that has not happened). As [with this] he does not clearly say that he regrets that he swore - that we should consider it duress - but rather that his will today is like it was at the beginning, but he [just] wants it annulled now. How is this? He swears that he not benefit from x and [x] becomes the town scribe or butcher, and he says, "My will [still] stands that I did not want to benefit from him and I [also] did not want him to become the scribe or the butcher." We do not annul [it] for him until he says, "Since I see that this man has become the scribe, I regret that I swore [off] his benefit forever. And if only I had not sworn!" In this way, we annul [it] for him; as behold, he concedes that his will has changed and that he regrets his deeds completely, due to the lack of his knowledge - as had he known at the time of the oath what he knows today, he never would have sworn. And it is like duress. And we expound (Shevuot 26a), "'A man with an oath' (Leviticus 5:4) - to exclude duress."

And it is written about impurity of the Temple and its consecrated foods (Leviticus 5:2), "Or a soul that touches anything impure, etc. and it was hidden from him"; and it is stated about it all at the end of the matter (Leviticus 5:6), "And he shall bring his guilt-offering." And the verse does not come explicitly that the liability of the impure one there would be with his entering the Temple or with his eating consecrated meat. Rather, we have understood from the tradition that it speaks about this (Shevuot 6b). And even though the thing is from the tradition, we have found the liability for excision for one who ate consecrated [food] or entered the Temple explicit in another place, as it is stated (Leviticus 7:20), "And the soul that eats meat from the sacrifice of the peace-offering that is to the Lord and his impurity is upon him, he shall be excised"; and another verse (Numbers 19:20) states about the impure one that enters the Temple, "for the Temple of the Lord he has made impure, and he shall be excised." And once excision has been written about its volitional transgression, there is a sacrifice for its inadvertent transgression - with our rule, that everything that is with excision for its volitional transgression, is with a sin-offering for its inadvertent transgression. And it is written about an oath of expression (Leviticus 5:4-6), "Or if a soul swears to express with his lips, etc. and it was hidden from him, etc. And he shall bring his guilt-offering." And from where [do we know] that the liability there [for them] is with a sacrifice that varies up and down? As it is written in the section (Leviticus 5:11), "And if his hand does not reach, etc."

To not swear falsely: To not swear falsely, as it is stated (Leviticus 19:12), "And you shall not swear in My name falsely." And they, may their memory be blessed, explained (Shevout 21a) that this verse warns about an oath of speech. And an oath of speech is what is stated in the Torah (Leviticus 5:4), "Or a soul that swears to express with the lips to do bad or to do good." And it is divided into four parts - two of the future and two of the past, such as swearing on something that was done or not done, and on something that in the future he will do or will not do. And an oath of speech is only practiced with things that it is possible for a person to do, whether in the past or in the future. How is of the past? "I ate," or "I did not eat"; and so [too,] "I threw," or "I did not throw a stone into the sea." And how is of the future? "I will eat," or "I will not eat"; or "I will throw," or "I will not throw." But with things that have a prevention from the Torah, an oath of speech is not practiced. As an oath only rests upon an optional matter - that if he wants, he does it and if he wants, he does not do it - as it is stated, "to do bad or to do good." But with any matter of a commandment, there is an obligation upon him to do it. Therefore an oath of speech does not rest upon him, whether in the past or in the future - in the case that he swears to perform a commandment, and he did not perform it; and so [too,] if he swears that he performed a commandment, and he did not perform it. As [just] like a liability [for punishment for a false oath] does not rest upon the matter of a commandment in the future, so too does it not rest upon it in the past. And so is the matter elucidated in its place in Shevuot 27a.

And we can open to annul even with something that newly develops (nolad), so long as it is something that commonly develops. But with something new that does not commonly develop, [we do not]. So is it explained in the Gemara (Nedarim 64a). And so [too,] we can open with regret, and as Rava determines in the name of Rav Nachman in Tractate Nedarim 22b - "We open for regret, and make ourselves available to annul, even to the one who has sworn by the God of Israel," which is a severe oath. And [this is] uniquely with regret from the beginning, such as "Is this heart [still] upon you?" [This is] meaning to say that this vower vowed out of anger, and after his mind settled down, he is completely bewildered by his oath and does not want it at all. But if he regrets [it] now because of something new that developed after he vowed, and he wanted his vow until now; this is not effective regret, and we do not open for him at all - as behold, everyone who comes to ask about his vow certainly regrets it now. And if [this type of regret were effective], the Gemara would not have required us to search to find openings for vows. But we find in the Gemara that they did search for openings for vows. But rather the truth is certainly like we wrote, that we need regret from the beginning. And [this is the case] also, since the entire foundation of annulling vows is the claim of error or duress (Shevuot 26a), since the Torah stated (Leviticus 5:4), "a man with an oath" - to exclude duress; and so too, that his mouth and heart are the same. And if so, it is impossible to have mistake or duress during the time of all the oaths depend upon regret from now. But there is a claim of mistake or duress with regret from the beginning; as behold, he now admits that if he knew this, he would not have made the vow from the beginning.