Komentarz do Powtórzonego Prawa 20:7

פן ימות במלחמה [LET HIM GO AND RETURN] LEST HE DIE IN THE WAR — The meaning is: let him return so that he not die, for if he will not hearken to the words of the priests he deserves death (Sifrei Devarim 194:5).

פן ימות במלחמה, “lest he die in battle.” The Torah refers to his premature death. This is clear proof that all the people who die in battle died before the time allocated as their life span at birth. We have still more direct proof of this in Samuel I 26,10: ”or his ‘day’ will come and he will die, or he will go down to battle and will die.”

For if he does not follow the instructions of the kohein etc. I.e., he certainly returns in order to protect those [who return because of their transgressions], etc. [Therefore] if the kohein told him to return and he does not return, he transgresses the words of the kohein and deserves to die in battle because of this sin, and this goes according to the opinion [of R’ Yosi Hagalili] that there is no death without sin. This answers why [in some texts] Rashi explains “lest he die in battle” at the end and not according to the order of the text that is written in the verses, because he is explaining according to [the view of] R’ Yosi Hagalili. (In the name of the Maharitz, and this is similar to Re”m’s explanation).