Midrash for Numbers 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.

Our masters said “It is written about Joshua (in Josh. 1:5), ‘as I was with Moses, so I will be with you.’ So Joshua should have lived a hundred and twenty years like Moshe our teacher. And why were they shortened by ten years? Because at the time that the Holy One, blessed be He, said to Moses (in Numb. 31:2), ‘Exact vengeance for the Children of Israel […],’ even though the announcement of [his] death was [also] announced, he did not delay the thing. Rather, he showed alacrity, [as stated] (in Numb. 31:6), ‘And Moses sent them.’ But Joshua did not do like this. When he came to war against thirty-one kings, he said, ‘If I kill them, I will die immediately, as happened to Moshe our teacher.’ What did he do? He began to stall in the war with them, as stated (in Josh. 11:18), ‘Joshua waged war with all those kings over a long period.’ [So] the Holy One, blessed be He, said to him, ‘This is what you did? See that I will shorten your years by ten years.’ Solomon said (about this in Prov. 19:21), ‘Many thoughts are in the heart of a man, [but it is the counsel of the Lord that will stand].’”

Rabbi Phineas said: The Holy One, blessed be He, said to Moses: Do ye remember what those Midianites did to you, for twenty-four thousand men fell in Israel? But before "thou art gathered in," arise, execute vengeance, (as it is said,) "Avenge the children of Israel of the Midianites; afterwards shalt thou be gathered unto thy people" (Num. 31:2).

Another opinion: “The Lord tests the righteous.” – This is Abraham – “Sometime after these things, God tested Abraham.” R. Avin expounded: (Ecclesiastes 8:4) “Since a king's word is supreme, who can say to him: ‘What are you doing?’” – R. Avin said: [This may be compared] to a teacher who commands his student, saying to him: (Deuteronomy 16:19) “You shall not judge unfairly,” but [the teacher himself] judges unfairly; (Deuteronomy 16:19) “Do not take a bribe,” but [the teacher himself] takes a bribe; Do not lend on interest, but [the teacher himself] lends on interest. His student said to him: Rabbi, you said to me: Do not lend on interest, but you lend on interest? [Is it] permitted to you but forbidden to me? [The teacher] said to him: I said to you: Do not lend on interest to a Jew, but you may lend on interest to an idol worshipper, as it is written: (Deuteronomy 23:21) “You may lend on interest to a foreigner, but you may not lend on interest to your brother [Israelite].” Thus Israel said before The Holy One Blessed be He: Master of the Universe, you wrote in your Torah: (Leviticus 19:18) “You shall not take vengeance or bear a grudge,” but you take vengeance and bear a grudge, as it is said: (Nahum 1:2) “The Lord is vengeful and fierce in wrath. The Lord takes vengeance on His enemies.” The Holy One Blessed be He said to them: I wrote in the Torah: (Leviticus 19:18) “You shall not take vengeance or bear a grudge against your countrymen,” but I take vengeance against idol worshippers – (Numbers 31:2) “Avenge the Israelite people on the Midianites.” It is written: (Deuteronomy 6:16) “Do not test the Lord” – [but] “God tested Abraham.”

(Bamidbar 31:2) "Afterwards you will be gathered unto your people": We are hereby apprised that Moses' death was contingent upon the defeat of Midian — in spite of which he entered into it with zeal, viz. (Ibid. 3) "And Moses spoke to the people, saying 'hechaltzu,'" connoting zeal, as in (Devarim 3:18) "Chalutzim shall you cross over." (Ibid.) "And let them be against Midian to execute the vengeance of the L-rd against Midian": He told them: You are not executing the vengeance of flesh and blood, but the vengeance of Him who spoke and brought the world into being, as it is written (Nachum 1:2) "the L-rd is a G-d of scorn and revenge."