The Torah in Parashat Bo presents the basic laws relevant to the Pesach celebration, including the command to observe the first and seventh days of the holiday as Yom Tov, when constructive work is forbidden: “On the first day [of Pesach] there shall be a sacred occasion, and on the seventh day there shall be for you a sacred occasion; no melakha shall be performed on them” (12:16).
The Mekhilta, cited by Rashi, notes the passive form used by the Torah in issuing this command: “no melakha shall be performed.” The implication, the Mekhilta explains, is that not only is it forbidden for one to actually perform melakha (work) on Yom Tov, but one may also not instruct somebody else to perform melakha.
This comment by the Mekhilta led the Semag (lo ta’aseh 75) to the conclusion that amira le-nokhri – instructing a gentile to perform melakha on one’s behalf on Shabbat or Yom Tov – constitutes a Torah prohibition. Whereas it is generally assumed that this prohibition was enacted by the Sages, and asking a gentile to perform melakha does not violate Torah law, the Semag draws proof from the Mekhilta that this indeed constitutes a Torah violation.
Later authorities questioned this view, noting the Gemara’s explicit comment in Masekhet Shabbat (150a) classifying this prohibition as “shevut” – a Shabbat prohibition enacted by the Sages. Indeed, the clear consensus among the halakhic authorities is that amira le-nokhri is forbidden only on the level of rabbinic enactment, and is therefore subject to certain leniencies (Mishna Berura 243:5).
Different approaches have been taken among the Acharonim to reconcile the view of the Semag with the Gemara’s explicit characterization of amira le-nokhri as a rabbinic prohibition. One possibility is suggested by the Maharam Shick, in one of his published responsa (O.C. 100), where he notes the debate among the Tanna’im as to whether one may indirectly extinguish a fire on Shabbat. The Mishna in Masekhet Shabbat (120a) cites the view of Rabbi Shimon ben Nanas allowing one to place utensils with water in the path of a fire in order to indirectly extinguish it. Rabbi Yossi, however, forbids doing so. Earlier in Masekhet Shabbat (47b), the Gemara comments that this debate revolves around the question of “geram kibui” – indirectly extinguishing a fire on Shabbat. Rabbi Yossi maintains that the Torah prohibition of extinguishing on Shabbat makes no distinction between direct and indirect extinguishing, whereas Shimon ben Nanas maintains that indirect extinguishing is not forbidden on the level of Torah law, and is therefore allowed for the sake of avoiding significant damage to property. The Shulchan Arukh (O.C. 334:22) codifies the view that “geram kibui” is permissible on Shabbat (and the Rama adds that this is allowed only when necessary to prevent a significant financial loss; there is considerable discussion among the poskim as to whether the Shulchan Arukh also accepts this limitation).
The Maharam Shick suggests that the status of amira le-nokhri would depend upon this debate regarding “geram kibui.” According to Rabbi Yossi’s view, that even indirectly extinguishing a fire on Shabbat constitutes a Torah violation, any form of indirect melakha would likewise be forbidden on the level of Torah law. Conceivably, then, Rabbi Yossi would view amira le-nokhri – performing a melakha by proxy, so-to-speak, by asking a non-Jew to perform the act in question – as a Torah prohibition. The Maharam Shick thus explains that the Mekhilta, which characterizes amira le-nokhri as a Torah violation, expresses the view of Rabbi Yossi, and the Semag, evidently, followed this opinion. When the Gemara classifies amira le-nokhri as a rabbinic prohibition, it expresses the view of Rabbi Shimon ben Nanas, according to whom only direct acts of melakha are forbidden on the level of Torah law. As mentioned, this is the view accepted as normative Halakha, and thus the consensus among the halakhic authorities is that amira le-nokhri is forbidden only by force of rabbinic enactment.