Midras Keluaran 3:12: Mekhilta DeRabbi Yishmael, Shemot Rabbah, Midrash Tanchuma & Midrash Tanchuma Buber

"by way of the land of the Philistines, for it was near": Near (i.e., "close") is the thing of which the Holy One Blessed be He spoke to Moses (Exodus 2:12): "When you take the people out of Egypt, you will serve G–d on this mountain." Variantly: "for it was near": It afforded easy return to Egypt, viz. (Ibid. 5:3) "Let us go a three days' distance in the desert." Variantly: "for it was near": Close (in time) was the oath that Abraham had sworn to Avimelech, viz. (Genesis 21:23) "And now, swear to me here by G–d that you will not deal with me falsely (by trespassing on my land), or to my son or my grandson," and his grandson was still alive. Variantly: "for it was near": The first war (that with Egypt) was too close to the second (that with Canaan). Variantly: "for it was near": The Canaanites had only recently acquired the land, and (Genesis 15:16) "And they (the Israelites) shall return here in the fourth generation, for the sin of the Amorites is not yet complete."

“Moses said to God: 'Who am I, that I should go to Pharaoh, and that I should take the children of Israel out of Egypt?’” (Exodus 3:11)
“Moses said to God: Who am I [anokhi]?” Rabbi Yehoshua ben Levi said: This is analogous to a king who married off his daughter and committed to give her one province and gentlewoman as a maidservant, and he gave her a Kushite maidservant. His son-in-law said: ‘Didn’t you commit to give me a gentlewoman as a maidservant?’ So, Moses said before the Holy One blessed be He: ‘Master of the universe, when Jacob descended to Egypt, didn’t you say this to them: “I [Anokhi] will descend with you into Egypt and I [Anokhi] will take you up” (Genesis 46:4), and now you say to me: “Go now, and I will send you to Pharaoh”? It is not I [anokhi] about whom you said: “And I [Anokhi] will take you up.”’¹²Moses is, as it were, pointing out to God that He promised to take Israel out of Egypt Himself, and not by means of an agent.
Another interpretation: Rabbi Nehorai says: Moses said before the Holy One blessed be He: ‘You say to me: Go and take Israel out. Where do I shelter¹³Following Rabbi David Luria’s emendation mashkinam rather that mashkim. them in the summer due to the sun, and in the winter due to the cold? From where do I provide food and drink? How many birth mothers are among them, how many pregnant women, how many children are among them, how many types of foods have you provided them to sustain them, how many delicacies have you prepared for the pregnant women, how much toasted grain and how many nuts have you provided for the children?’ Where is this matter explicated? It is in Song of Songs, as it is stated: “Tell me, whom my soul loves…” (Song of Songs 1:7). The Holy One blessed be He said to him: ‘The bread that came out with them from Egypt will suffice them for thirty days; you know how I am destined to lead them.’
Another interpretation: “Who am I?” – He [Moses] said before Him: ‘Master of the universe, how am I able to enter a place of robbers and a place of murderers? That is: “Who am I, that I should go to Pharaoh…” “And that I should take the children of Israel out” – what merit do they possess that will enable me to take them out?’ The Holy One blessed be He said to him: “Because I will be with you” (Exodus 3:12). One says “I will be with you” only to someone who is afraid.
“He said: Because I will be with you, and this is your sign that it is I who sent you: When you take the people out of Egypt, you will serve God upon this mountain” (Exodus 3:12).
“And this is your sign that I sent you” – and in this manner it will be apparent that you are My emissary, because I will be with you and anything you wish I will perform.
“When you take the people out of Egypt, you will serve God upon this mountain.” That which you said: ‘With what merit will I take them out of Egypt?’ Know that due to the merit of the Torah that they are destined to receive through you on this mountain they will emerge from there.
Another matter: “[you will serve] God” – what is it that He said to him: “That I [anokhi] sent you”?¹⁴Why does the verse change from first person to third person? “This is your sign that it is I who sent you…you will serve God.” Our Rabbis of blessed memory said: A sign of the first deliverance is that Israel went down to Egypt with anokhi, as it is stated: “I [anokhi] will go down with you to Egypt” (Genesis 46:4), and with anokhi I will take you up. A sign of the ultimate redemption is that with anokhi they will be cured and are destined to be delivered, as it is stated: “Behold I [anokhi] will send you Elijah the prophet” (Malachi 3:23).

Why was the Torah not given as soon as the Israelites departed from Egypt? He did not do so because He had said to Moses: After you bring the people out of Egypt, serve God on this mountain (Exod. 3:12). R. Judah the son of Shalum said: This may be compared to a king’s son who has just arisen from a sickbed. His father says: “We will wait three months so that he may recuperate completely from his illness before we take him to the teacher’s home to study the law.” Similarly, when the Israelites departed from Egypt there were among them men who had been injured in their labors, and so the Holy One, blessed be He, said: I will delay giving them the Torah until they are healed.