Midras Mazmur 78:20: Shemot Rabbah, Otzar Midrashim, Midrash Tanchuma & Eikhah Rabbah

“The Lord said to him further: Put your hand in your bosom. He put his hand in his bosom and took it out, and behold, his hand was leprous, like snow” (Exodus 4:6).
“The Lord said to him further: Put your hand in your bosom.” He said to him: ‘It is just like the serpent who, when he engaged in slander, I afflicted him with leprosy, as it is stated: “Cursed [arur] are you from all the animals” (Genesis 3:14), as you say: “Malignant [mameret] leprosy”’ (Leviticus 13:51). Rabbi Elazar said: Those spots on it [the serpent] are leprous marks; so do you deserve to be afflicted with leprosy. Why did he place it in his bosom? It is because slander is typically told in secret. Likewise it says: “He who slanders his neighbor in secret, I will destroy [atzmit]” (Psalms 101:5). Atzmit [refers to] nothing but leprosy, as it is stated: “In perpetuity [litzmitut]” (Leviticus 25:23), which is translated as completely [laḥalutin]²⁹In Targum Onkelos. and it is taught: “The difference between a quarantined leper and a confirmed leper [muḥlat] is only… (Megilla 8b).”³⁰The midrash cites the mishna to show that the word muḥlat, which is derived from the same root as laḥalutin, is used in the context of leprosy.
“He put his hand in his bosom and took it out, and behold, his hand was leprous, like snow.” He received his due because he engaged in slander. Rabbi Yehoshua of Sikhnin said in the name of Rabbi Levi: From here you learn that anyone who suspects another of something which is untrue of him, is afflicted in his body.
“He said: Put your hand back in your bosom. He put his hand back in his bosom; and he removed it from his bosom, and behold, it was restored like his flesh” (Exodus 4:7).
“He said: Put your hand back in your bosom.” How is there a sign for Israel in this? [It is as if God were saying:] Go and say to them: Just as a leper causes impurity, so do the Egyptians render you impure. And just as he [the leper] is purified, so is the Holy One blessed be He destined to purify Israel, as it is written: “And behold, his hand was leprous, like snow,” and in the healing it is written: “He removed it from his bosom, and behold, it was restored like his flesh.” Our Rabbis say: So as not to cast aspersions on Moses’s flesh [i.e. his bosom]; therefore, his hand was not afflicted with leprosy until he removed it from his bosom. However, regarding the healing, it was healed in his bosom. Alternatively, from here punishments are delayed before being exacted upon the righteous, while the [divine] attribute of goodness takes effect quickly.
“And it shall be that if they do not believe even these two signs, and they do not heed your voice, you shall take from the water of the Nile and pour it out on dry land; and the water that you take from the Nile will become blood on the dry land” (Exodus 4:9).
“It will be, if they will not believe even these two…” Why did the Holy One blessed be He perform three signs for him? It is corresponding to Abraham, Isaac, and Jacob.
“You shall take from the water of the Nile.” He indicated to him that, by means of something he will say to Israel, the water is destined to be transformed into blood, and he will be punished through it [the water], as it is written: “Hear now, defiant ones” (Numbers 20:10), and he struck the stone and extracted [water], as it is stated: “Behold, He struck the rock, and water flowed out [vayazuvu]” (Psalms 78:20). Vayazuvu is an expression of nothing other than blood, as it is stated: “If a woman will have a flow [yazuv zov] of her blood” (Leviticus 15:25). That is why he struck the stone twice, as initially it produced blood and finally water. In the first two signs, you find that they were restored to their original state, but the sign of the blood was not restored to its original state because He did not wish to forgive Moses for the sin of the water. And how was there a sign for Israel in this? He said to them: ‘With this sign the Egyptians will be afflicted first.’

“Moses said to the Lord: Please my Lord, I am not a man of words, neither yesterday, nor the day before, nor since You spoke to Your servant; for I am slow of speech, and slow of tongue” (Exodus 4:10).
“Moses said to the Lord: Please my Lord [Adonai].”³¹The name of the Lord is spelled alef, dalet, nun, yod. Moses said to the Holy One blessed be He: ‘You are the lord [adon] of the world, and it is me you want to be an emissary? “I am not a man of words…”’ The Sages said: Seven days previously, the Holy One blessed be He was inducing Moses to go on His mission, but he did not want to go until the incident at the bush. That is what is written: “I am not a man of words,” one; “yesterday,” two; “neither [gam],” three; “the day before,” four; “nor [gam],” five; “since,” six; “You spoke,” seven.
“The Lord said to him: Who makes a man's mouth, or makes a man mute, or deaf, or sighted, or blind? Is it not I, the Lord? Now, go, and I will be with your mouth, and teach you what you shall speak” (Exodus 4:11-12).
Rabbi Pinḥas HaKohen said; Moses said: ‘I am not a man of words, and I do not see [how] words [can be effective] here, because the person to whom I am going [Pharaoh]³²Presumably, Pharaoh is regarded as a slave because Ham is the ancestor of Egypt and the descendants of Ham are cursed with slavery. See Genesis 9:25. Alternatively, “the man” refers to the typical Israelite slave. is a slave and he does not accept admonition, as it is stated: “A slave will not be admonished with words” (Proverbs 29:19). <variant reading:="" if="" i="" am="" not="" going="" to="" afflict="" him,="" i="" will="" not="" go,="" immediately:="" “the="" lord="" said="" [to="" him:="" who="" makes="" a="" man's="" mouth,="" or="" makes="" a="" man="" mute,="" or="" deaf,="" or="" sighted,="" or="" blind?="" is="" it="" not="" i,="" the="" lord?]”="">. If I am going to afflict him I will go immediately.’

"I lost the three shepherds in one month" (Zecharia 11:8); and thus, in one month, Aaron, Miriam, and Moses died. Miriam died on the 1st of the month of Nisan, and the well closed up; and in the second of Nissan, Aaron's sons died; On the first of Av, Aaron died, and the clouds of glory dissipated; On the seventh of Adar Moses our teacher, and God's servant, died. Even though they didn't all die in the same month, it's considered as if it were one month. Each had a gift that they gave to the Israelites. By the merit of Miriam, God gave the well, by the merit of Aaron, the clouds of glory, By the merit of Moses, the Mana. When Miriam died, the well closed so the Israelites could see that it was by her merit that God granted them the well. Moses and Aaron bewailed her internally, and the Israelites did so publicly. Moses didn't know about the Israelites mourning until after six hours, when the Israelites came to them and said: "how long will you sit and mourn?" He said to them "should I not continue to mourn my sister who has died." "They said to him: "just as you mourn for one soul, all the more so mourn for all of us." He said to them: "why" They said to him "because we do not have water to drink." He stood and went and saw that there was no water in the well, and he began to argue with them, he said:"did I not say to you that I can't carry this people on my own, did I not appoint for you officers for the thousands, and officers for the hundreds, and the fifties, and the twenties, I gave you officials, and chiefs, and great elders, and they are to busy themselves with your problems." They said to him: "Everything is on you, for you are the one who brought us out of Egypt and brought us to this terrible place, if you give us water, everything will be fine, but if you don't, then we will stone you." When Moses heard this, he fled from them and went into the tent of meeting. God said to him "Moses what is going on?" Moses said before the Master of the World: "your children want to stone me, and were I not to have fled, I would have already been stoned to death." God said said: "how long will will you speak ill of my children, was it not enough for you that I told you at Horeb, just a little more and they will stone you. Now go and pass before them and see whether they will actually stone you, and it is said the Torah: "God said to Moses, pass before the people." Moses went first and his cohort after him, and Moses didn't know which rock God had intended to give to them for bringing out water. The Israelites found a rock that was dripping, and they stood upon it. When Moses saw them standing on it, he turned around and said to God "how long will you put our lives at risk?" He said to them, "until I bring water out of the rock." The Israelites said: "give us water so that we can drink!" Moses responded to them "How long will you continue to rebel? Does a creation rebel against its creator? As such, you are rebelling against God. Moses said: "God wants to give you water." The Israelites said: "you are the prophet who shepherds us in the dessert and now you say you don't know which rock God intends you to bring water out of? Moses and Aaron gathered the people around a different rock, as it says in the Torah "Moses and Aaron gathered the community at the face of the rock." Moses said to himself: "If I command the rock to bring out water and it doesn't, I'll be embarrassed before the community, and they will say to me, 'Moses, where is your alleged wisdom.'" At the very same moment Moses told the Israelites, "you know that God can do miracles for you, and you know that miracles are beyond me. For when the knowledge of man is divinely inspired, it is not his own knowledge or wisdom. Moses brought down his staff upon the back of the rock, and he did so himself, as he spoke to the israelites , as it says in the Torah "from this rock, we will bring you water." The rock began to fill itself to bring out water, and when Moses saw it, he lifted his arm again and struck the rock, as it says in the Torah "he hit the rock twice with his staff." This time though, blood came out, as it says in the Psalms, "yes, he hit the rock and the waters flowed (Psalm 78:20)." It's a flow of blood, as we see from the laws of menstruation "when a woman has a discharge of blood (Leviticus 15:25)." Moses came and said to God "the rock isn't bringing out water, only blood." God said to the rock: "why are you only bringing out blood, and not water?" The rock said "Master of the Universe, why did Moses hit me?" God then asked Moses, "why did you hit the rock?" Moses responded: "In order to bring out water." God said: "Did I tell you to hit the rock? Did I not tell you to speak to it with words?" Moses responded: "I did speak to it, but nothing came out!" God responded "did you not command all of Israel "in justice you shall judge your people (Leviticus 19)? Thus, why didn't you judge the rock with justice? This is how I raised you in Egypt, as it says in scripture 'God fed him honey from the rock, (Deuteronomy 32:13).' It befits you to lead, and thus say to my children "listen you rebels!" Don't read "rebels" rather "idiots" shotim (also a hominem for drinkers). They are idiots, and you have your eyes open. A nation of idiots will not enter the land of Israel, as it says in the Torah "you will not bring this community . . ." Therefore God said to Moses, "tell the rock to turn it's blood into water." It is thus written in scripture: "who turned the rock into a pool of water, the flinty rock into a spring (Psalm 114:8)." (Note this is a Psalm recited during Hallel on Rosh Chodesh, the beginning of the month). When they reached the beginning of the month, God said to Moses, "your time has come to an end." Moses said before him, "please God, let it not be soon." "It is tomorrow" responded God, thus Moses was distressed all day, for he didn't know when exactly his death would come. ...