Midras Ulangan 3:24: Midrash Tanchuma Buber, Mekhilta DeRabbi Yishmael, Devarim Rabbah & Midrash Tanchuma

(Deut. 3:24:) YOU HAVE <ONLY> BEGUN <TO SHOW YOUR SERVANT YOUR GREATNESS AND YOUR MIGHT…. > He said to him: You are the one who opened a door for me to pray to you.³Sifre to Deut. 3:24 (27). When? When they did that deed.⁴I.e., when they made and worshiped the golden calf. See Deut. 9:7–12. The Holy One said to him (in Deut. 9:14): LET ME ALONE, AND I WILL DESTROY THEM AND BLOT OUT THEIR NAME FROM UNDER THE HEAVENS. Moses said: Who would seize hold of the Holy One? One only seeks to pray for one's children. What is written there (in Exod. 32:11)? AND MOSES IMPLORED THE LORD HIS GOD. Moses said: Once I prayed for the community and was answered, but the community prayed for me and was not answered. Why? Because you have issued a decree over me <for calling them rebels>! But you were the one who began by calling them <rebels> (in Numb. 17:25 [10]): <PUT BACK AARON'S ROD … > TO BE KEPT AS A SIGN FOR THE CHILDREN OF REBELLION. Then because I called them <rebels> (in Numb. 20:10): LISTEN, YOU REBELS, you said (in 20:12): THEREFORE YOU SHALL NOT LEAD THIS CONGREGATION <INTO THE LAND THAT I HAVE GIVEN THEM>.

and, in the end, Moses arose and implored (that he be permitted to enter the land, etc.), viz. (Devarim 3:24) "And I entreated the L–rd at that time, saying, etc." An analogy: A king decrees that his son not enter his palace with him. He enters the first door and he is met with silence; and so, the second. At the third, he is rebuked and told: It is enough for you until here. Similarly, when Moses conquered the land of the two nations, Sichon and Og, and he gave it to Reuven and Gad and the half tribe of Menasheh, he said: It seems to me that the decree (of the L–rd) is conditional,

“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.