Before us is Mishnah 1 of the first chapter of tractate Nedarim. To understand the Mishnah, we need to introduce two concepts that it deals with: yados (handles) of vows, and kinuyim (substitute expressions) of vows.
The two basic concepts:
The primary way of making a vow is for a person to declare about a given object that it should be forbidden to him like a korban (a sacrifice). A korban is something that a person takes and whose status he changes through the words of his mouth, and by force of his speech it becomes forbidden, since from now on it belongs to the Beis HaMikdash and is brought as an offering. On this foundation the two concepts are built:
A yad (handle) of a vow - instead of saying the complete formula, that this object should be forbidden to him like a korban, the person says: let there be a vow upon me regarding this object that I will not eat it, and he does not finish his words with "like a korban." Such an incomplete statement is called a yad, that is, a handle of a vow.
A kinuy (substitute expression) of a vow - the person does state the matter of the korban, but instead of the word "korban" itself he uses a different term.
These two concepts apply not only to vows, but also to nezirus, to an oath, and to a cherem (a ban), which is likewise a type of vow.
The words of the Mishnah:
"Kol kinuyei nedarim k'nedarim" - all the substitute expressions for vows have the same law as a vow itself, and they have the power to render the object forbidden to the person. However, words are missing here in the Mishnah, and this is a case of chisurei mechasra: we must also read "kol yedos nedarim k'nedarim" - that the handles too, the abbreviated formulations of a vow, are considered a vow. The Mishnah will go on to bring examples of both cases.
And this is not said with regard to vows alone:
"Vacharamim k'charamim" - the substitute expressions for a cherem are likewise a cherem. The cherem is described in the Torah in the book of Vayikra as something whereby a person takes an object and forbids it, in the sense that from now on it is pledged to the Beis HaMikdash or given to the kohanim.
"Ushevuah k'shevuah" - the substitute expressions for an oath are like an actual oath, and so too its handles.
"Unezirus k'nezirus" - here too, both the substitute expressions and the handles of an acceptance of nezirus have the same law as nezirus.
Handles of vows:
The Mishnah first describes examples of handles of vows that are considered vows. One who says to his fellow one of the following openings:
"Mudarni mimach" - I am vowed away from you, that I will derive no benefit from you at all.
"Muframi mimach" - I am separated from you.
"Merucheikni mimach" - I am distanced from you.
And he attached to them the second half of the sentence - "she'eini ochelach" - that I will not eat of yours, or "she'eini to'amach" - that I will not taste of yours - it is forbidden, and he may not derive any benefit from his fellow. In all these cases the correct way would have been to conclude by saying "like a korban," and since he did not conclude that way, it is considered a handle of a vow.
"Menudeh ani lach":
This statement can be understood in two ways: from the language of distancing and removal, "I am removing myself from you," which as we said is a form of a handle of a vow; or from the language of niduy, excommunication, that is, the form of ban that a beis din imposes, which has no connection at all to a vow and whose statement carries no meaning in this context. And since there is no certainty as to the intent of the words, "Rabbi Akiva hayah chocheich bazeh l'hachmir" - he would press his lips together out of uncertainty, and he ruled stringently that it is forbidden.
A vow versus a voluntary gift:
The next part of the Mishnah distinguishes between two types of people and two types of expression. The very idea of making a vow is not looked upon favorably by Chazal, and therefore an upright Jew will not want to make a vow, even though he can make a nedavah, a voluntary gift. And what is the difference between them? With a korban, one who wishes to bring an animal as an offering and does so by way of a vow, that is, through a verbal commitment that he will bring an offering in the future, is in a dangerous position, for if he does not fulfill his commitment he will be guilty of a serious sin. For this reason making a vow is not considered a good idea, and an upright Jew does not act this way; whereas one whom the Mishnah calls wicked - a harsh term, but this is the language of the Mishnah and the Gemara - would be careless enough to make a vow.
A nedavah, by contrast, means that a person takes an animal without any verbal commitment, brings it to the Beis HaMikdash, and there makes it an offering. He does not take anything upon himself, but merely declares that this animal is going to be an offering. This way is safer, and it is the way an upright Jew takes. And since this is so, the term "upright ones" is associated with a nedavah.
"K'nidrei resha'im":
The Mishnah now applies the terms neder and nedavah, the one to the wicked and the other to the upright, in order to create various commitments. One who says "k'nidrei resha'im" - like the vows of the wicked, that is, in the manner that the wicked vow - "nadar b'nazir uv'korban uvishvuah" - this wording is effective for all three:
Nezirus: a nazir passes before him and he says "I am like the vows of the wicked" - since this was said as a nazir passed before him, it is considered an acceptance of nezirus, for a vow is something the wicked do, and this statement indicates his wish to be a nazir.
Korban: his animal is standing there, and he says "like the vows of the wicked upon me," in the manner that the wicked vow so shall I take upon myself - this is a vow to bring an offering.
Shevuah: a loaf of bread is lying there, and he says "like the vows of the wicked that I will not eat of it" - this is an oath, and he binds himself with it.
It is worth clarifying the difference: a vow forbids the object, whereas an oath is a prohibition that a person imposes upon himself not to perform an action. It emerges that the expression "the vows of the wicked" serves as an effective expression for accepting nezirus, for making an object into an offering, and for making an oath not to do something.
"K'nidrei ksheirim" and "k'nidvos ksheirim":
One who says "k'nidrei ksheirim" - like the vows of the upright - who indeed used the word "vows" but attached it to the upright rather than to the wicked - "lo amar klum" - he has said nothing, and his words do not take effect, for the upright do not make vows but voluntary gifts.
But one who attaches the upright to a nedavah, and says "k'nidvos ksheirim":
Regarding nezirus: if he said that he should be a nazir like the voluntary gifts of the upright - this is an effective expression for accepting nezirus upon himself, for at times even upright Jews accept nezirus in a special manner and under special circumstances.
Regarding a korban: here too a commitment of the nedavah type takes effect, the kind that the upright make, and therefore his statement is effective to make the animal an offering.
Regarding an oath: it is not effective and his statement has no force, for the upright do not swear under any circumstances, and therefore "like the voluntary gifts of the upright" is not an effective expression for an oath.
In summary: in this Mishnah we learned the two concepts that open Maseches Nedarim - handles and substitute expressions - whose law is that of the vow itself, and likewise with regard to bans, oaths and nezirus. We saw examples of handles: "mudarni mimach," "muframi mimach" and "merucheikni mimach" together with "she'eini ochelach" or "she'eini to'amach"; Rabbi Akiva's uncertainty regarding one who says "menudeh ani lach," about which he was hesitant and ruled stringently; and the distinction between a vow, which is the way of the wicked, and a voluntary gift, which is the way of the upright - and from here, that one who says "like the vows of the wicked" has vowed with regard to nezirus, a korban and an oath, one who says "like the vows of the upright" has said nothing, and one who says "like the voluntary gifts of the upright" has made an effective statement regarding nezirus and a korban, but not regarding an oath.