Commentaire sur Le Deutéronome 20:2

כקרבכם אל המלחמה [IT SHALL BE] WHEN YE COME NIGH UNTO THE BATTLE, [THAT THE PRIEST … SHALL SPEAK] — i.e. when ye are on the point of leaving the ספר — the boundary of your land (Sifrei Devarim 191).

ונגש הכהן, “the priest shall approach;” this is the משוח מלחמה, the priest anointed for this task in war. ודבר אל העם, “and he shall address the people,” in Hebrew (Sotah 42).

Near your departure, etc. Rashi is answering [the question]: Scripture should have written, “And as you go out to battle”! Therefore he explains, “Near, etc.” You might ask, how does Rashi know it means near the border? Perhaps it means actually drawing near to the battle? The answer is since it is written in the next verse, “Hear, Yisroel, [you are setting out today to battle], etc.,” this indicates that [the Torah] already mentions it [drawing near to battle]. [If so], why does the verse say “as you near etc”? This must mean that when they are near the border the kohein makes these conditions. See Sotah (42a).