When treating on Shabbat a patient who is critically ill, or when dealing with an individual whose life is in danger – known in Hebrew as pikuach nefesh – one is commanded to "violate" the Shabbat. This applies even if there's a doubt whether it is – or could evolve into – a life threatening situation.

Even if retroactively it becomes clear that the act was unnecessary, or didn't accomplish its goal, it is not considered a desecration of the Shabbat, and the individual who acted receives reward for attempting to save a life.

In all these matters, if one is in doubt about the correct mode of behavior, it is better to err on the side of violating the Shabbat, rather than potentially putting a life in danger.

When a sage attends to pikuach nefesh it serves as a lesson as to the immense privilege it is to save a lifeOne who is faced with a situation that might be construed as a matter of pikuach nefesh, and goes to consults with a rabbi about the situation is considered a murderer1—because due to his excessive "piety," and the resultant delay in implementing the proper measures, he might be endangering a life. And the rabbi who is asked is disgraceful—because he should have taught his community the proper manner of action when dealing with pikuach nefesh, i.e., to take action without delay.2

When it is necessary for the sake of pikuach nefesh to disregard the Shabbat laws, it does not matter who violates the Shabbat; the one who's able to perform the task most quickly should do so, and whoever does so is praiseworthy.

If there are several people who can attend to the endangered individual, it is preferable that the Shabbat "desecration" be done by the greatest Torah-scholar and the most pious person present. When a sage attends to pikuach nefesh it serves as a lesson as to the immense privilege it is to save a life.3 Needless to say, one may not seek to be "ultra-religious" by asking a gentile to desecrate the Shabbat for the sake of pikuach nefesh.4

Some more details:

  • Any procedure which is necessary to perform for the patient, but it is clear that it does not at all need to be performed on Shabbat, should be delayed until after Shabbat.5
  • If a person is ill before Shabbat and he will need care on Shabbat that will include acts forbidden on Shabbat, one should prepare whatever possible before Shabbat to minimize or eliminate the need to desecrate the Shabbat.6
  • In order to desecrate the Shabbat, one must be convinced that there is at least a certain measure of doubt that the case involves pikuach nefesh.7 In situations where during the week people do not react with a sense of immediate urgency, one may not desecrate Shabbat.8
  • One may only disregard the Shabbat laws when there is an existing situation that might involve pikuach nefesh; e.g., an elderly patient fell and needs to be rushed to the hospital.
  • The laws of Shabbat may also be violated in anticipation of a potential life-threatening situation, provided that it is highly reasonable to assume that indeed it is an immediate concern.9 Example: If the machines in an intensive care unit are not functioning, they must be fixed on Shabbat even if at the moment there is no knowledge of a patient requiring life-support.
  • That said, far-fetched hypotheses such as "I need to travel on Shabbat to university to pursue my medical studies, since one day I'll save lives with my medical expertise," or, "I need to go shopping for a sweater on Shabbat because it's supposed to be cold and I might catch pneumonia and die..." do not qualify as pikuach nefesh. 10
  • Elective operations, or other elective procedures warranting a stay in a hospital, should not be scheduled for the second half of the week (i.e., Tuesday night and on).11
  • Community-wide risks and concerns are determined using broader parameters of pikuach nefesh. Consequently, Jewish ambulance volunteers might be permitted to carry their radios on Shabbat. Likewise, security patrols in Israel might not required to wait until they hear about a terrorist attack in order to operate metal detectors in public places (an expert rabbi should be consulted in cases such as these).