I often hear people use the phrase “bli neder” which I understand means something like “without an oath”. I’m confused as to why people say this, when it applies and when not. Not understanding this and trying to use the phrase myself has been awkward, so any light you could shed on this would spare me more embarrassment. Thanks.
Technically speaking, a neder is a very specific form of obligation, but is colloquially used to refer to all verbal commitments made using the various terminologies for oaths. The laws of the different forms of oaths are very complicated and beyond our scope. So I’ll discuss only the reason and customs behind the phrase “bli neder” used commonly in conversation, as you’ve heard.
A neder is the Hebrew word which is commonly used to refer to an oath that is binding and which obligates a person to do some deed, whereby abrogation of the neder makes one accountable by Heaven for not fulfilling that oath. Therefore, people take the possibility of speaking under oath and its consequences very seriously.
The basic idea is that our power of speech is so great that if we commit to do something as an oath, this promise is spiritually recorded and creates an obligation which hovers over a person until he fulfills his pledge. If he doesn’t, the obligation is exacted from him in the form of punishment.
Accordingly, the reasoning behind making the qualification “bli neder” is to exempt a person from any possible obligation or ensuing punishment for not keeping his word.
Let’s first explore cases where this qualification is not relevant in order to properly understand when saying “bli neder” is warranted.
Usually, expressing a willingness or commitment to do something mundane would not oblige a person to do it without the person’s verbally stating some term relating to oaths. So saying, for example, “I will go to the store” would not require a person to do so, nor would he be held accountable for not going. Saying “bli neder” in this type of scenario would be nonsense.
Conversely, actions which are either required as mitzvot or forbidden as aveirot are not subject to oaths at all (Y. D. 139:4, 6). In the case of a mitzvah, making a neder does not create any special obligation since he’s already obligated by the Torah, independent of the neder. Similarly, in the case of a prohibition, making an oath to sin,
So when is saying “bli neder” appropriate?
When there is some non-obligatory, voluntary mitzvah aspect to his commitment. So, going back to the example of saying he’ll go to the store, if it’s in the context of helping someone, where there is a non-obligatory element of the mitzvah of chesed, one should qualify his pledge to go to the store with the phrase “bli neder” to indicate that his expression of goodwill should not be mistaken as a binding oath.
Similarly, if he makes a voluntary monetary pledge, or even if the pledge is required but the amount is not, for example when making an aliya to the Torah, a person should qualify the pledge by saying “bli neder” in order to avoid the consequences of his good word becoming obligatory as an oath.
In summary, the general rule of thumb for using the phrase “bli neder” in conversation is that it doesn’t apply for mundane acts which don’t have some aspect of mitzvah, nor does it apply to situations of either explicit mitzvot or transgressions; rather it applies to something that has some voluntary element of mitzvah where verbally expressing a willingness to do it may be construed as an oath, such that saying “bli neder” negates that possibility.