The first Mishna in the massekhet teaches that a person does not need to use a specific formula to make a neder – a vow – but that kinuyim, which are substitutes for the formal language of a vow, will also be effective. This is true in other cases where a person makes a statement that has significance according to the, like taking a shevua – an oath – or accepting the status of a nazir upon oneself.
What is the difference between a neder and a shevua? The Gemara explains that in a neder, the statement made by the person takes effect on the object – e.g., when a person takes a vow not to eat a certain food, the food is now forbidden. A shevua, on the other hand, takes effect on the person, so that now there is a prohibition on the person to eat the food.
The conceptual distinction between the object (the heftza) and the person (the gavra) has become a popular method of distinguishing in many areas of mitzvot and. Nevertheless, the basic question that needs to be dealt with is what actual difference is there if a given prohibition is applied to the object or to the person. Several suggestions are put forward by the rishonim:
The Ran and Tosafot suggest that in a case where the language is mixed up and a person takes a shevua that an object is forbidden or takes a neder that he will refrain from a given activity, the oath or the vow will not take effect since the statement was an incorrect one. In fact, this very question is dealt with in the Talmud Yerushalmi, and the majority opinion is that a neder cannot use the language of a shevua or vice versa.
Not all are in agreement with this conclusion. The Ramban rules that such mistaken language would create an obligation because it would be considered to be yadot nedarim – literally “handles” to a neder – abbreviated forms that create a neder even if the language is not precise.