Kommentar zu Bamidbar 31:2

מאת המדינים [AVENGE THE CHILDREN OF ISRAEL] OF THE MIDIANITES — but not of the Moabites, for the Moabites entered into the matter out of fear, because they feared that they might plunder them, since about them it was stated only, (Deuteronomy 2:9) “Do not contend with them in battle”; but the Midianites, however, had got excited (had interfered) in a quarrel that did not concern them. Another explanation of why God forbade them to wage war against the Moabites, and which explains at the same time why they had been forbidden to wage war against the Ammonites (cf. Deuteronomy 2:19): because, said He, of the two goodly doves (virtuous women) which I am to bring forth from them, — Ruth the Moabitess, and Naamah the Ammonitess [Solomon's wife] (Bava Kamma 38b).

AVENGE THE CHILDREN OF ISRAEL OF THE MIDIANITES; AFTERWARD SHALT THOU BE GATHERED UNTO THY PEOPLE. It was decreed upon our teacher Moses not to cross over the Jordan, but on the other [eastern] side of the Jordan he fulfilled all the commandments [that were necessary] for Israel. Thus he conquered the two great Amorite kings, and divided their land up as an inheritance [amongst the tribes of Reuben, Gad, and half of the tribe of Menasheh], and it was he who was worthy of executing vengeance upon the enemies of the Eternal, leaving Joshua only the commandment of [conquering and dividing] the Land. Furthermore [this commandment was given to Moses because] the Holy One, blessed be He, gave him honor so that the righteous shall rejoice when he seeth the vengeance,⁵⁹Psalms 58:11 — Since the Midianites had enticed the people of Israel to immorality and the worship of Baal-peor (see Ramban above Balak 25:1 and Pinchas 25:11) the triumph of right over evil was thus a source of rejoicing to the righteous one [Moses]. this being the meaning of afterward shalt thou be gathered unto thy people. And Moses showed honor to Phinehas⁶⁰Verse 6. because he had begun the meritorious task [of punishing the Midianites, by killing Cozbi]⁶¹Above, 25:15. and it was up to him to finish it, and therefore he appointed him the anointed priest for this war.⁶²See Deuteronomy 20:2. It was not fitting that Eleazar should go [as the anointed priest of the war], because he was the High Priest [after the death of Aaron].⁶³Above, 20:28 — The position of the anointed priest of the war was always distinct from that of the High Priest (see Rambam, Hilchoth Klei Hamikdash, Chapter 3). Hence “it was not fitting,” as Ramban expresses it, that Eleazar the High Priest should go with the army and function in the role of the anointed priest of the war.

נקם נקמת, "avenge the Israelites, etc." The plain meaning of the verse is that G'd delegated Moses to carry out this task. How is it possible then that he did not even accompany the soldiers into battle? Although I have explained previously that the vengeance Moses took consisted of telling the people to launch this campaign, the plain meaning of the verse cannot be ignored. Who allowed Moses to send Pinchas instead when G'd had told him to take vengeance? Furthermore, why did the Torah make Moses' death depended on the completion of this punitive expedition?