Numbers 31:6

אתם ואת פינחס [MOSES SENT THEM … TO THE WAR], THEM AND PHINEAS — The repetition of the word אתם, “them”, in association with Phineas’ name tells us that Phineas was regarded as equal to all of them together. — But why did Phineas go and Eleazar did not go? The Holy One, blessed be He, said, “He who made a beginning with this meritorious work, in that he slew Kozbi the daughter of Zur (who was a Midianitess), let him complete it”. — Another explanation why Phineas and not Eleazar went is that he went to take vengeance for Joseph, his mother’s ancestor, as it is said, (Genesis 37:36) “And the Midianites sold him [unto Egypt]”. And from where do we know that Phineas’ mother was of the family of Joseph? Because it is said, (Exodus 6:25) that she was “one of the daughters of Putiel” (see Rashi on that verse) — which is explained to mean that she was of the seed of Jethro who used to fatten (פטם) calves for idolatrous worship, and of the seed of Joseph who overcame (שפטפט, who talked or argued with) his passions (cf. Sifrei Bamidbar 157:4; Sotah 43a). — Another explanation: Phineas went because he was the high priest anointed for war purposes (cf. Deuteronomy 20:2 and Rashi thereon) (Sotah 43a). וכלי הקדש AND THE VESSELS OF HOLINESS … [WERE WITH THEM] — these were the Ark and the Golden Plate (which are termed קדש, “holiness”, in Numbers 4:20 and Leviticus 8:9 respectively) (cf. Sifrei Bamidbar 157:4; Sotah 43a). — Because Balaam was with them (the Midianites) and through enchantment he made the kings of Midian float in the air and he himself floated with them, he (Phineas) showed them (held up to them) the Golden Plato upon which the Divine Name was engraved and they immediately fell to the ground. On this account it is said (v. 8) of the Kings of Midian that they were killed “upon those belonging to them who had been killed”, meaning that they fell from the air upon those who had already been killed; and similarly of Balaam it is written in the book of Joshua (13:22): “[And Balaam the son of Beor did the children of Israel slay] upon those who were slain by them” (Midrash Tanchuma, Matot 2; Talmud Yerushalmi Sanhedrin 10:2). בידו means IN HIS POSSESSION (not actually “in his hand”, for it was impossible for him to hold these sacred objects in his hand), similar to (21:26) “And he took all his land from his possession (מידו)” (Sifrei Bamidbar 157:4).

And Moshe sent them to the war, a thousand of every tribe, them and Pineĥas the son of El῾azar the priest, to the war, with the holy instruments, and the trumpets to blow in his hand.

וַיִּשְׁלַ֨ח אֹתָ֥ם מֹשֶׁ֛ה אֶ֥לֶף לַמַּטֶּ֖ה לַצָּבָ֑א אֹ֠תָ֠ם וְאֶת־פִּ֨ינְחָ֜ס בֶּן־אֶלְעָזָ֤ר הַכֹּהֵן֙ לַצָּבָ֔א וּכְלֵ֥י הַקֹּ֛דֶשׁ וַחֲצֹצְר֥וֹת הַתְּרוּעָ֖ה בְּיָדֽוֹ׃