Nedarim 15

Stay awake.

A mishnah at the bottom of yesterday’s daf states:

One who says “Sleeping is forbidden for me,” “Speaking is forbidden for me,” or “Walking is forbidden for me,” or one who says to his wife, “Engaging in sexual intercourse with you is forbidden for me,” — he is obligated by: He shall not profane his word. (Numbers 30:3)

This mishnah is surprising and, for the Gemara, a problem. We have learned previously that vows apply only to objects of substance. But sleep, speech, walking and sex are actions, not objects. Why then would the mishnah then suggest that a vow to abstain from any of these is effective?

Today’s Gemara suggests that the language of the mishnah is elliptical. The full language of the vow must actually be this:

Sleeping is forbidden for my eyes.

Eyes are objects, so a vow about them can take effect.

There’s another problem with the mishnah’s hypothetical vow to abstain from sleep: It might be impossible to keep. After a lengthy period of wakefulness, a person will eventually fall asleep involuntarily. So what should we make of a vow to stay awake indefinitely?

And if he did not give a measurement (i.e. a limit on his vow of sleeplessness) do we let him be until he inevitably transgresses the prohibition, He shall not profane? But didn’t Rabbi Yohanan say: For an oath that I will not sleep for three days, he is flogged, and he may sleep immediately.

It is considered largely impossible for a person to stay awake for 72 hours. (Please don’t try it.) Therefore, if someone makes a foolish vow to do just that, his vow is considered vain and the court orders him flogged as punishment. His vow does not take effect and he may go straight to sleep.

For these two reasons — because the vow must be about an object and because the vow must be achievable — the Gemara reasons that the mishnah cannot mean exactly what it says. Rather, it must really be talking about a person who vows as follows:

Sleep is forbidden to my eyes tomorrow if I sleep today.

That is, if I sleep today, I may not sleep tomorrow. This version of the vow is manageable, if unpleasant, and also conforms to the rule that vows must reference an object. Of course, the Gemara points out, the inverse could also be what the mishnah is referring to:

Sleeping is forbidden to my eyes today if I sleep tomorrow.

This is a more slippery vow, because the prohibition is based on a future action. The rabbis are split over whether we should forbid the one who makes this vow to sleep today, so that he cannot possibly violate the vow by sleeping the next day, or whether he should be permitted to sleep today, and we trust him to stay awake tomorrow so that he will not violate the vow.

If this all seems like an unnecessarily complicated reading of the mishnah, you’re not alone in thinking so. Ravina suggests a much simpler reading, namely, that the person who vows to abstain from sleep has made a vow whose transgression is only a violation of rabbinic law, not Torah law.

All this might seem an abstruse academic exercise in making a mishnah written hundreds of years earlier conform to a later rabbinic understanding of vows. And in some ways, it is. But it also serves as a demonstration of the rabbinic commitment to the texts of their forebears, and their approach to solving the challenges those texts present.

When a mishnah feels instinctively wrong to later generations, that “problem” becomes an opportunity for discussion and reinterpretation. The later rabbis might not arrive at a reading that solves all the problems, but the discussion itself opens the door to deeper ruminations about human nature and the contours of vowing: Can we expect the person who sleeps today to stay awake tomorrow to fulfill the terms of his vow? Will people really vow to stop sleeping indefinitely? Should we even let them make such a detrimental and ultimately unattainable vow? 

One thing is certain: The rabbis would prefer you did not try this at home.

Read all of Nedarim 15 on Sefaria.

This piece originally appeared in a My Jewish Learning Daf Yomi email newsletter sent on November 9th, 2022. If you are interested in receiving the newsletter, sign up here.

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