Despite the great severity of the prohibition against desecrating Shabbat, an action defined as lifesaving [pikuah nefesh] overrides Shabbat. In other words, if in order to save a life one must desecrate Shabbat, it is permitted and even a mitzva to do so.

Two explanations are given for this principle (Yoma 85b). The first is fundamentally logical: “Desecrate one Shabbat for him so that he can observe many Shabbatot.” It is worth having the holiness of one Shabbat desecrated in order for a sick person, for example, to recover and observe more Shabbatot. Another explanation is based on the verse, “You shall observe My statutes and My ordinances, which a man shall perform and live by them” (Leviticus 18:5). The Sages interpret the term “live by them” to mean “and not die by them.” This means that almost all commandments in the Torah are overridden in life-threatening situations. The exceptions are the three most serious offenses: idolatry, severe sexual violations such as adultery or incest, and murder.

The category of pikuah nefesh includes possibly life-threatening situations. That is, even when there is only a concern for the person’s life, and there is no certainty that his life is indeed in danger, this is also considered pikuah nefesh. It is also permitted to desecrate Shabbat even if it is not clear that the actions performed for the endangered person will in fact save his life.

Further reading: For more on the sanctity of life and saving lives, see A Concise Guide to the Sages, pp. 6, 150.

Further reading: For more on the elevated status of a person and the entire world on Shabbat, see A Concise Guide to Mahshava, p. 36ff.