Parashat Acharei-Mot concludes with the section of arayot, which lists the various kinds of sexual relationships which the Torah forbids. In the introduction to this section the Torah admonishes, “You shall observe My commands and My statutes which a person shall perform and live by them” (18:5). The Gemara (Sanhedrin 74a) famously understands the phrase “va-chai bahem” (“and live by them”) in this verse as indicating that God does not wish us to die as a result of observing His commands. This verse thus establishes the famous rule of piku’ach nefesh, whereby the concern to rescue human life overrides the Torah’s laws.
A number of Acharonim have noted the irony in the fact that this rule is alluded to by the Torah specifically here, in the introduction to the section of arayot. Sexual offenses are among the group of three exceptions to the rule of piku’ach nefesh, as one is required to surrender his life when this is necessary to avoid a forbidden sexual relationship (such as if an enemy threatens to kill somebody if he refuses to engage in relations with a family member or another man’s wife). This prohibition, like idol-worship and murder, is not waived for the sake of protecting human life, in contradistinction to the vast majority of Torah laws. It might therefore strike us as surprising, and odd, that the Torah would establish the principle of piku’ach nefesh specifically in the context of arayot – one of the three sins regarding which this principle does not apply.
Several answers have been offered to this question, one of which emerges from the comments of Tosefot (Sanhedrin 74b) regarding the verse “va-chai bahem.” Tosefot assert that fundamentally, there should be no reason for the Torah to inform us the rule of piku’ach nefesh. The premise that God does not want us to surrender our lives for the sake of observing His laws is, essentially, intuitive and self-understood. The only reason why it was necessary for the Torah to specify “va-chaim bahem,” that we suspend its laws for the sake of human life, is because of the extraordinary requirement of martyrdom to avoid transgressing one of the three aforementioned sins (murder, idolatry and sexual immorality). Since there are three Torah laws for which one must be prepared to surrender his life, one might have assumed that this standard applies to all the Torah’s laws. It is for this reason, Tosfot explain, that the Torah informs us “va-chaim bahem,” that protecting human life overrides all but three of the Torah’s commands.
This perspective might help explain why the provision of “va-chai bahem” appears in the introduction to the section dealing with the arayot. The unique stringency of arayot, which must be observed even at the risk of death, is what gives rise to the possibility that all Torah laws override the concern for human life. And thus specifically in this context, the Torah specified “va-chai bahem,” that with but three exceptions, its laws are waived when human life is at risk.
(See Or Ha-chayim to Vayikra 18:5, and Rav Chaim Leib Eisenstein’s Peninim Mi-bei Midresha, Parashat Acharei-Mot.)