Sefer HaChinuch ספר החינוך

The commandment to anoint a priest for war: That we were commanded to anoint one priest with anointing oil and to appoint him to speak with the people at the time of war, and this priest is called, “the anointed for war.” And from this commandment is that the anointed priest should say three verses that are mentioned in the Torah to the people at the time of the war: “Whoever is a man that planted a vineyard, etc. And whoever is a man that built a house, etc. And whoever is a man that has taken (married) a woman, etc.” (Deuteronomy 20:5-7). And he adds further words of his own [that] arouse people to war and uplifts them to endanger themselves to assist the religion of God and protect it, and to take vengeance upon the fools that destroy the arrangements of the states. And so did they, may their memory be blessed, say in Tractate Sotah 43a, “‘And the officers shall speak’ — the priest speaks and the officer makes it heard.”

The root of this commandment is well-known — since the men of the war need strengthening at the time of war and since a man is heeded more when he is honored, the Torah commanded that the one appointed to strengthen [the troops] be from the priests, who are the select of the people. And the matter that we send back from the war whoever planted a vineyard and did not eat from it, or betrothed a woman but did not [marry] her or built a house but did not dwell in it — and so [too,] the one who is afraid from the sins in his hand — this thing too is appropriate and fit, since all of these people are very weak from [what is needed] to go into war; as their thoughts are very occupied with the things mentioned in Scripture, and they would disincline the hearts of their fellows — and like the matter that is written explicitly (Deuteronomy 20:8), “and that the heart of his brothers not melt like his heart.” And so [too,] is it fit to send back the one who is afraid from the sins in his hand, lest others be killed from his iniquity. And all of the paths of the Torah are uprightness and faithfulness.

From the laws of the commandment — that which they, may their memory be blessed, said (Sotah 44b) that we only send back from the battle lines those mentioned in Scripture in an optional war, but in a commanded war, everyone goes out [to war], even a groom from his room and a bride from her canopy; and that which they said (Mishneh Torah, Laws of Kings and Wars 7:4) that after all those sent back from an optional war are sent back, those left arrange the battle lines and appoint army leaders at the front of the people and position strong sentries at the back of all the battle lines [with] iron axes in their hands, and they have the authority in their hands to cut off the shins of anyone who seeks to leave from the war, since the beginning of [an army] falling is fleeing; and the rest of its details — are elucidated in Tractate Sotah. (See Mishneh Torah, Laws of Kings and Wars 6,7.)

And this commandment is practiced by males at the time that the Land of Israel is in its inhabitation. And this is one of the commandments that is incumbent upon all of the community. And if the people transgressed this, such that they did not appoint an anointed priest among them — as per what we mentioned — and he did not speak the things mentioned in Scripture to the people, they have violated this positive commandment.