מדרש אויף בראשית 14:18

“Lord God, You have begun to show Your servant Your greatness and Your mighty hand, for what god is in the heavens or on the earth who can act in accordance with Your actions and according to Your mighty deeds” (Deuteronomy 3:24).
“Lord God, You have begun” – what is “Lord God”? Rabbi Yehoshua ben Korḥa said: In two places, Moses likened himself to Abraham, but it was to no avail for him. How so? The Holy One blessed be He called to Abraham, and he said: “I am here,” as it is stated: “And said to him: Abraham; and he said: I am here” (Genesis 22:1). What is “I am here”? I am here for priesthood, I am here for kingship; and he merited priesthood and kingship. From where is it derived that he merited priesthood? As it is stated: “The Lord has taken an oath, and He will not renounce it; you are priest forever by My decree, like Malkitzedek” (Psalms 110:4).¹⁰Malkitzedek was a priest (see Genesis 14:18). He merited kingship, as it is stated: “To the valley of Shaveh, which is the valley of the king” (Genesis 14:17).¹¹The midrash understands this as an allusion to the fact that the kings of the region elected Abraham as their king (see Bereshit Rabba 42:5).
Moses, too, sought to do so, as it is stated: “He said: Moses, Moses; and he said: I am here” (Exodus 3:4). I am here for priesthood; I am here for kingship. The Holy One blessed be He said to him: “Do not glorify yourself before a king, and do not stand in the place of the great” (Proverbs 25:6). “Do not approach [tikrav] here [halom]” (Exodus 3:5). You have no involvement with the priesthood, as it is stated: “The stranger who approaches [hakarev] shall be put to death” (Numbers 3:10). You have no involvement with the kingship, as it is stated: “That You have brought me here [halom]” (II Samuel 7:18).¹²David used the term halom in reference to the kingship.
Abraham said: “Lord God, what will You give to me?” (Genesis 15:2). Rabbi Levi said: He said before Him: ‘Master of the universe, if through justice¹³The name “God” represents the attribute of justice. I deserve to have children, give them to me; if not, give them to me through mercy.¹⁴The name “the Lord” represents the attribute of mercy. The Holy One blessed be He said: ‘As you live, you deserve them’: “And, behold, the word of the Lord was to him…[one who will emerge from your loins, he will be your heir]” (Genesis 15:4). Moses, too, said so: “Lord God, You have begun” – if through justice I deserve to enter the Land of Israel, let me enter; if not, let me enter through mercy. The Holy One blessed be He said to him: “Do not glorify yourself before a king…” “As you will not cross this Jordan” (Deuteronomy 3:27) – when Moses saw how resolute the matters were, he began speaking harsh words.¹⁵He began praying in a more forceful manner, as the midrash will detail in the next section.

R. Zechariah said in the name of R. Ishmael: "The Holy One, praised be He! desired to bring forth priesthood from Shem (son of Noah), as it is said (Gen. 14, 18) And Malkizedek, king of Salem, brought bread, and wine, and he was a priest of the most high God, but since he preceded the blessing of Abraham to that of the most Holy One, the Lord [decided] to bring it forht from Abraham, as it is said (Ib., ib., 19) and blessed be the most high God; i.e., Abraham said to Shem: 'Is it proper to utter the blessing of a servant before the blessing of his master?' Therefore it (priesthood) was brought forth from Abraham, as it is said (Ps. 110, 1) By David a psalm. The Eternal said unto my Lord, etc.; and immediately after this is written. The Lord hath sworn, and will not repent of it, thou shalt be a priest forever after the words of Malkizedek, i.e., on account of the words of Malkizedek. And this is the meaning of the passage (Gen. 14, 18) And he was a priest of the most high God; i.e., he was a priest, but not his children."

“Take the Levites in place of all the firstborn among the children of Israel, and the animals of the Levites in place of their animals; the Levites shall be Mine, I am the Lord” (Numbers 3:45).
“Take the Levites…” – our Rabbis said: Why did the Holy One blessed be He command to redeem the firstborn of Israel with the Levites? It is because initially the firstborn were performing the sacrificial service, until the tribe of Levi arose, as our Rabbis taught: Until the Tabernacle was established, private altars were permitted and the sacrificial service was performed by the firstborn. From the establishment of the Tabernacle, private altars were prohibited and the sacrificial service was performed by the priests.⁷ Zevaḥim 112b. Know that the firstborn were sacrificing until the tribe of Levi arose; take proof from the beginning of the creation of the world. Adam the first man was the firstborn of the world. When he sacrificed his offering, as it is stated: “May it please the Lord more than a bull with horns and hooves” (Psalms 69:32), he donned the vestments of the High Priest, as it is stated: “The Lord God made for Adam and for his wife hide tunics, and clothed them” (Genesis 3:21). They were praiseworthy garments, and the firstborn would perform the service in them. When Adam died, he bequeathed them to Seth. Seth gave them to Methuselah. When Methuselah died, he bequeathed them to Noah. Noah arose and sacrificed an offering, as it is stated: “He took from every pure animal…[and offered up burnt offerings]” (Genesis 8:20).
Noah died, and he bequeathed them to Shem. Was Shem the firstborn? Was it not Yefet who was the firstborn, as it is stated: “Brother of Yefet the eldest” (Genesis 10:21)? Why, then, did he bequeath them to Shem? It is because Noah foresaw that the line of the patriarchs would be established from him. Know that Shem would sacrifice, as it is stated: “And Malkitzedek⁸Commenting on this verse, Rashi quotes a midrash (perhaps from Bereshit Rabba 56) that identifies Malkitzedek with Shem the son of Noah. king of Shalem…[he was a priest of God the Most High]” (Genesis 14:18). Was priesthood granted to him? Priesthood was not given until Aaron stood. What is it that it says here: “He was a priest”? It is because he would sacrifice like priests.
Shem died, and he bequeathed it to Abraham. Was Abraham the firstborn? Rather, because he was righteous, the birthright⁹I.e., the status of firstborn. was passed to him and he sacrificed, as it is stated: “He offered it up as a burnt offering in place of his son” (Genesis 22:13). Abraham died, and bequeathed it to Isaac.
Isaac arose and gave it to Jacob. Was Jacob firstborn? It is, rather, that you find that Jacob took it from Esau cunningly. He said to him: “Sell me your birthright today” (Genesis 25:31). Do you think, perhaps, that it was for nothing that Jacob said to Esau that he should sell him the birthright? No. It is, rather, that Jacob sought to sacrifice, but he could not because he was not a firstborn. Esau said: What do I want with this birthright, as it is stated: “Esau said: Behold, I am going to die, [and why do I need a birthright]” (Genesis 25:32). At that moment, Ezekiel’s prophecy applied in his regard and said to him: “Surely, you hated blood, and blood will pursue you” (Ezekiel 35:6). Did Esau hate blood? Did he not kill several righteous men, did he not kill several pious men, and it says: “Surely, you hated blood, and blood will pursue you”? Rather, he said to him: ‘Surely, you hated the blood of an offering,’ as he was firstborn, and the firstborn sacrifice. Therefore, “blood will pursue you.” At that moment, when Jacob acquired the birthright, he began sacrificing, as it is stated: “God said to Jacob: Arise, ascend to Beit El…and make there an altar…” (Genesis 35:1).
Likewise, when Moses sacrificed at Sinai, it was the firstborns who sacrificed, as it is stated: “He sent the lads of the children of Israel, [and they offered up burnt offerings]” (Exodus 24:5). Who are the “lads”? They were the elite of the firstborn. “They offered up burnt offerings” – you learn that no person would sacrifice other than the firstborn.
When Israel performed that deed,¹⁰They sinned with the Golden Calf. they said: Let the firstborn come and sacrifice offerings before it, as it is stated: “They arose early the next day, and they offered up burnt offerings and they presented peace offerings” (Exodus 32:6). God said to them: ‘I promoted the firstborn, and I rendered them prominent in the world, but they rejected Me and arose and sacrificed before the calf. I will remove the firstborn and bring in the children of Levi.’ Therefore, God said to Moses that he should count them, as it is stated: “Count the children of Levi” (Numbers 3:15).
Rabbi Yehuda HaLevi said: Who whispered to you that God removed the firstborn from sacrificial rites and appointed the children of Levi, as it is stated: “Take the Levites”? In place of whom? “In place of all the firstborn among the children of Israel, and the animals of the Levites in place of their animals; the Levites shall be Mine, I am the Lord.” The Rabbis said: To what is this matter comparable? To a provincial money changer regarding whom a matter of corruption was attributed. The king knew, and said to his governor, ‘remove him and appoint another in his place.’ Nevertheless, that money changer is found to be obligated to repay a debt. The king said: Let the one who inherited his place repay his debt. So, the firstborn were prominent in the world, but arose and sacrificed before the calf. God said: Let the firstborn depart, and let the children of Levi enter. Nevertheless, the firstborn incurred liability to be eliminated. God said: Let the Levites come and redeem them. Therefore, you find the Levites redeeming the firstborn. That is what is written: “Take the Levites…”
“And the animals of the Levites in place of their animals” – because priests and Levites are exempt from redeeming their firstborn, the firstborn of man and the firstborn of a donkey, [the latter of] which is likened by the verse to the firstborn of man, as it is written: “However, you shall redeem [the firstborn of man], and the firstborn of an impure animal you shall redeem” (Numbers 18:15). But they are not exempt from [redeeming] the firstborn of a pure animal, as it is sacred. What is, “the Levites shall be Mine, I am the Lord”? I am trustworthy to pay them a good reward because they sanctified My Name at the time of the calf.