Deuteronômio 21:10 Halacá: Gray Matter I & Kitzur Shulchan Arukh

While the Rambam does mention Levi's military exemption at the end of Hilchot Shemitah Veyoveil, it is uncertain how much weight this carries, because he does not present this rule in Hilchot Melachim, where he discusses military exemptions at length. In fact, the Radak (II Shmuel 23:20) claims that in wars against the enemies of Israel, even the Kohanim (the most sanctified part of the tribe of Levi), who ordinarily avoid contact with dead bodies, must take an active part in killing the enemy.²From the Radak's comment in I Melachim (2:25), it sounds as if he only believes that Kohanim are permitted (but not obligated) to take part in fighting enemies. However, he writes there that he is merely restating what he wrote in II Shmuel 23:20. David's great warrior, Benayahu ben Yehoyada, exemplified this practice. Despite being a Kohein, he served as a high-ranking officer in King David's army and eventually became the head of King Shlomo's army. Moreover, the Gemara (Kiddushin 21b) and the Rambam (Hilchot Melachim 8:4) discuss the laws of a Kohein who fights in wars, indicating that this was done in practice.³The Talmud discusses whether a Kohein is permitted to take an eishet yefat to'ar (see Devarim 21:10-14).

Beginning with the Shabbos following Tishah beAv and after that, for the next seven Shabbosos we read the haftoras "sheva denechamasa" [seven haftoras of consolation]. If the first day of Rosh Chodesh Elul occurs on Shabbos, the haftorah, Aniyah so'arah, is set aside ["O you afflicted, floundering in the storm,"] (Isaiah 54:11) and we read instead, "Hashamayim kis'i," [The heaven is My throne] (Isaiah 66:1), because this haftorah also contains consolation for Jerusalem. On the Shabbos of Parshas Ki Seitzei, when the haftorah Roni akarah [Sing, O barren woman] (Isaiah 54:1) is read, we conclude the haftorah with Aniyah so'arah, which is next to it. If, by mistake, on Shabbos Rosh Chodesh Elul, you said Aniyah so'arah, and you became aware of it before saying the concluding berachos, you should also say Hashamayim kis'i, and then say the concluding berachah. If you only became aware [of your error] after saying the concluding berachos, then you should recite, Hashamayim kis'i without the berachos. If Rosh Chodesh Elul occurs on Sunday, the haftorah, Machar Chodesh is set aside, [Tomorrow is Rosh Chodesh] (I Samuel 20:18), because it contains no consolation for Jerusalem, and the haftorah Aniyah so'arah is read.