Halakhah su Numeri 5:20

The Sefer Hachinuch (425) writes that if someone has the opportunity to kill a member of the seven Canaanite nations without endangering himself, failing to do so violates the mitzvah to destroy them (Devarim 7:10). The Minchat Chinuch (a commentary on the Sefer Hachinuch) finds the Sefer Hachinuch's ruling puzzling. Why should this mitzvah only apply when there is no danger involved? Although most mitzvot do not require that we sacrifice our lives to fulfill them, here the Torah requires us to do battle with the seven nations. It is understood, the Minchat Chinuch points out, that the Torah's laws do not assume that a miracle will occur (as explained by the Ramban's comments to Bemidbar 5:20 and 13:2). Since the normal course of the world is that people die in battle, we see that the Torah commands us to fight with the seven nations even at risk to ourselves.²Although the Minchat Chinuch concludes with an expression of some doubt, a number of Acharonim do embrace his argument, including Rav Naftali Tzvi Yehudah Berlin (Meromei Sadeh, Eruvin 45a and Kiddushin 43a) and Rav Yitzchak Zev Soloveitchik (Parshat Beshalach, p. 32; cited by Rav J. David Bleich, Contemporary Halakhic Probems 3:296-297).