Midrasch zu Tehillim 3:9

33 Another interpretation of (Numb. 21:17), "Then Israel sang": This is one of the three things that Moses said before the Holy One, blessed be He, and He said [back] to him, "You have taught me." He said in front of Him, "Master of the Universe, from where does Israel know what they did (was wrong)? Did they not grow up in Egypt? And all of Egypt are idolaters. And when You gave the Torah, You did not give it to them, and they were also not standing there, as it is stated (Exod. 20:18), 'And the people stood from afar.' And You only gave it to me, as it is stated (Exod. 24:1), 'And He said to Moses, "Ascend to the Lord.'" And when You gave the statements (Ten Commandments), You did not give [them] to them. You did not say, 'I am the Lord, your (plural) God'; but rather I am the Lord, your (singular) God. [Hence] You said it to me. Did I sin?" The Holy One, blessed be He, said to him, "By your life, you have spoken well. You have taught Me! From now on, I will say the expression, 'I am the Lord, your (plural) God.'" The second one is when the Holy One, blessed be He, said ( in Numb. 34:7), "visiting the iniquity of the parents upon the children": Moses said, "Master of the Universe, how many evildoers begat righteous ones; should they be removed by the iniquities of their parents? Terach was an idol-maker, but his son, Abraham, was righteous; so too Hezekiah was righteous, but Ahaz, his father was an evildoer; Josiah was righteous, but Amon, his father, was an evildoer. Is this proper, that the righteous be struck for the iniquities of their parents?" The Holy One, blessed be He, said to him, "Behold, you have taught Me! By your life, I will nullify My words and preserve your words, as it is stated (Deut. 24:15), ‘The parents shall not die for the children, and the children shall not die for the parents'; and it is by your life that I shall write [these things] in your name, as it is stated (II Kings 14:6), 'as it is written in the Torah of Moses, which God commanded ....'" The third one is when the Holy One, blessed be He, said to him, "Make war on Sichon; even if he does not want to engage with you, wage war with him, as stated (Deut. 2:24), 'Get up, go and cross the Arnon .'" But Moses did not do like this. Rather what is written above? "And I sent messengers" (Deut. 2:26). The Holy One, blessed be He, said to him, "By your life, I will nullify My words and preserve your words, as it is stated (Deut. 20:11), 'When you approach a town to attack it, you shall offer it terms of peace.'" Once Sichon did not accept, the Holy One, blessed be He, felled him in front of them, as it is stated (Deut. 20:33), "and we smote him." And not only that, but even [with] those that were hiding themselves in the caves to kill [the Israelites], the Holy One, blessed be He, signaled to the mountain and it crushed them, as it is stated (Ps. 74:13-14), "who smashed the heads of the monsters in the waters. It was You who crushed the heads of Leviathan." A common proverb says [that] if you gave bread to an infant, let his mother know. The Holy One, blessed be He, said, "From where will Israel know the favor I did for them?" What did He do? He distanced the mountains from each other and the streams swept down [the corpses], as it is stated (Numb 21:17), "And the streams poured." And the Israelites passed by and sang song - "then Israel sang" (Numb. 21:17). Israel said, "It is for You to do miracles for us, but it is for us to bless and laud Your name" - "Salvation is to the Lord; upon Your people is Your blessing, Selah" (Ps. 3:9). Upon the waters was it decreed against Moses, so he was not mentioned in the song. Moses said, "Master of the Universe, "I am dying because of them. You gave them the Torah from the wilderness, as it is stated, (Numb. 21:18), 'and from the wilderness, Matanah (which is also the word for gift).' And they possessed (nachalu) it from my hands, as it is stated (Numb. 21:19), 'And from Matanah, Nachliel.'" And from when they possessed it, You decreed death upon me, as it is stated (Numb. 21:19), "and from Nachliel, Bamot" - and from possession comes death (menachal, ba mot). "And from Bamot, Haggai in the field of Moav" (Numb. 21:20), as it is stated (Deut. 34:6), "And He buried him in the valley in the land of Moav." Job said, "He is not partial to princes; the noble are not preferred to the wretched; for all of them are the work of His hands" (Job 34:19).

(Bamidbar 18:8) "And the L-rd spoke to Aaron": I would think (the intent is) that the speaking was to Aaron; it is, therefore, written (Ibid. 17:5) "A sign for the children of Israel … as the L-rd spoke to Moses about him" (Aaron, viz., that only he and his sons are to be Cohanim), whereby we are apprised that the speaking was to Moses, to tell to Aaron. (Bamidbar, Ibid.) "And I, behold, (I have given to you") with joy, (the twenty-four priestly gifts.) These are the words of R. Yishmael — whereupon his disciples said to him: But master, it is written (Bereshit 6:17) "And I, behold, shall bring a flood of water, etc." Are we, then to assume that this was a joy to Him? He answered: When His angerers go lost from the world, it is a joy to Him. And thus is it written (Proverbs 11:10) "When the righteous prosper, the city exults, and when the wicked perish there is rejoicing." And (Psalms 3:9-10) "You have broken the teeth of the wicked. Deliverance is the L-rd's. Upon Your people are Your blessings, selah." And (Ibid. 10:16) "The L-rd is King for ever and ever. Nations have gone lost from His land." And (Ibid. 104:35) "Sinners will end from the earth, and the wicked will be no more. Bless the L-rd, O my soul, Hallelukah!" R. Nathan said to him: I will add to your words: "And I" — willingly; "behold" — with joy. And thus is it written (Shemot 4:14) "Behold, he (Aaron) is going out to meet you (Moses; and when he sees you, he will rejoice in his heart."