Midrash su Numeri 31:2

“Since the king's word has power, and who will say to him: What are you doing” (Ecclesiastes 8:4).
“Since the king's word has power.” Rabbi Bon said: It is written: “Do not test [the Lord]” (Deuteronomy 6:16), “and God tested [Abraham]” (Genesis 22:1), “Do not take vengeance and do not bear a grudge” (Leviticus 19:18), “the Lord is a zealous and vengeful God” (Nahum 1:2). [This is analogous] to a rabbi who would command his disciple, and say to him: ‘Do not divert judgment,’ but he [the rabbi] diverts judgment; ‘do not give preferential treatment,’ but he gives preferential treatment.²²A parallel midrash (Bereshit Rabba 55:3) adds the example: The rabbi tells him not to lend with interest, but he lends with interest. The disciple said to him: ‘Rabbi, for you it is permitted and for me it is prohibited?’ [The rabbi] said to him: ‘I am telling you only that you may not lend to an Israelite with interest, but lend to a gentile, as it is written: “You may take interest from a gentile” (Deuteronomy 23:21).’²³Thus, the rabbi informs his disciple that he did not fully understand any of the rabbi’s actions. So too, Israel said before the Holy One blessed be He: ‘Master of the universe, did You not write in Your Torah: “Do not take vengeance and do not bear a grudge” (Leviticus 19:18)? But You take vengeance and bear a grudge.’ He said to them: ‘I will not bear a grudge against Israel, as it is written: “He will not contend to eternity or forever bear a grudge” (Psalms 103:9); however, for the nations of the world: “The Lord is vengeful to His foes and bears a grudge against His enemies” (Nahum 1:2). I dictated to you in My Torah: “Do not take vengeance and do not bear a grudge against the members of your people” (Leviticus 19:18), but you may take vengeance against the nations of the world, as it is stated: “Avenge the children of Israel [on the Midianites]” (Numbers 31:2),’ to realize what is written: “Since the king's word has power, [and who will say to him: What are you doing].”

(Numb. 31:2) “Exact vengeance [for the Children of Israel on the Midianites; afterward you shall be gathered unto your people]”: R. Judah said, “If Moses had wanted to live for several [more] years, he could have remained alive; as the Holy One, blessed be He, had made his death dependent upon the vengeance against Midian. It is simply to show you the praise of Moses, as he said, ‘For the sake of my remaining alive, I shall delay the Children of Israel's vengeance on Midian?’ [Rather] immediately (in vs. 3), ‘Moses spoke unto the people, saying, “Arm some of your number (anashim) for the army, and let them fall on Midian.”’” [The word,] anashim, [implies that they were] righteous. So also elsewhere (in Exod. 17:9), “Choose anashim for us.”³Here also, as in Numb. 31:3, anashim implies that those chosen were righteous. And so too (in Job 4:13), “in the falling of slumber upon anashim.” (Numb. 31:3, cont.) “To render the vengeance of the Lord against Midian”: The Holy One, blessed be He, had said (in vs. 2), “the vengeance of the Children of Israel”; but Moses says (here in vs. 3), “the vengeance of the Lord.” The Holy One, blessed be He, said to them, “It is your judgment that is called for, because they caused Me to harm you.” [But] Moses said, “Master of the world, if we had been uncircumcised or practitioners of star worship or had denied [the binding force of] the commandments, they would not have persecuted us. But [they have done so precisely] because of the Torah and commandments which You have given. The vengeance, therefore, is Yours,” (as in Numb. 31:3), “to render the vengeance of the Lord against Midian.”

Another interpretation (of Numb. 31:2) “Exact vengeance for the Children of Israel.” This text is related (to Job 36:7), “He does not withdraw His eyes from a righteous person […].” What is the meaning of “He does not withdraw His eyes from a righteous person (literally, withdraw from a righteous person his eyes)?” The Holy One, blessed be He, does not keep back from a righteous person what he wants to see with his eyes. [The text] teaches that Moses longed to see vengeance on the Midianites before he died, and [so] he requested from the Holy One, blessed be He, about it, that he should [see it] with his eyes. Thus it is stated concerning Moses (in Ps. 58:11), “A righteous person will rejoice when he sees vengeance,” i.e., vengeance on Midian; “he will bathe his feet in the blood of the wicked person,” i.e., of Balaam. Moses said to Phinehas and the warring men, “I know that Balaam the Wicked is there, as he went to collect his wage. Before the wolf comes to the flock, spread the trap for him. And if you see that that wicked man is doing magic and is flying in the air […], show him the diadem, upon which it is written (according to Exod. 28:36), ‘holy to the Lord.’ And [when] he shall [then] fall, kill him.” (Numb. 31:8) “And upon their [other] corpses they killed the kings of Midian,” as they were doing magic with Balaam and flying in the air; so they showed them the diadem and they fell upon their corpses.