כ״א בסיון ה׳תשע״ה (June 8, 2015)

Nedarim 15a-b: A Vow Not To Sleep

We have already noted the basic difference between a neder and a shevua that is commented on by the Gemara. While a neder acts on an object (e.g. a person declares that meat is forbidden to him), a shevua acts on the person (e.g. he accepts upon himself a prohibition that will keep him from eating meat).

When examining the case of the Mishna (14b) where someone who takes a neder that he will not sleep is understood to be obligated by this pronouncement, the Gemara objects that “sleep” is not an object, and it can only become forbidden by means of a shevua (which will create a prohibition on the person keeping him from sleeping). In response, the Gemara offers the possibility of taking a neder forbidding one’s eyes from closing with sleep. In this case, since the neder is made on a specific object (his eyes) the neder will take effect.

Still the Gemara points out another difficulty with a vow against sleeping. If the person did not state a specific amount of time that he will not sleep, we know that Rabbi Yohanan teaches with regard to shevuot that a person who takes an oath not to sleep for three days is understood to have taken a false shevua – since it is impossible to go without sleep for 72 hours. Therefore, rather than forcing him to attempt the impossible we punish him immediately (for having made a false shevua) and allow him to sleep whenever he wants. Thus the Gemara is forced to offer an alternative case of neder, where the person in fact did limit the amount of time that he would keep his eyes from sleeping.

In theory it is possible for a person to go without sleep for a period of three days if he is constantly prodded and woken by others whenever he begins to doze off. Nevertheless, withholding sleep from someone for that length of time will likely cause long-term physical and psychological damage, which the Talmudic Sages could not condone.

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