The Lord (to Moses): Now you shall see what I will do to Pharaoh: for he shall let them go because of my strong hand, and he shall drive them out of his land because of my strong hand. (HCSB) I am the Lord. And I appeared to Abraham, to Isaac, and to Jacob, by the name of God Almighty, but by my name Jehovah I was not known to them. And I have also established my covenant with them, to give them the land of Canaan, the land of their pilgrimage, wherein they were strangers. And I have also heard the groaning of the children of Israel, whom the Egyptians keep in bondage; and I have remembered my covenant. Therefore say to the children of Israel, I am the Lord, and I will bring you out from under the burdens of the Egyptians, and I will rid you out of their bondage, and I will redeem you with an outstretched arm, and with great judgments: And I will take you to me for a people, and I will be to you a God: and you shall know that I am the Lord your God, which brings you out from under the burdens of the Egyptians. And I will bring you into the land, which I did swear to give to Abraham, to Isaac, and to Jacob; and I will give it to you for an heritage: I am the Lord.
Moses spoke so to the children of Israel. But they did not listen to Moses for anguish of spirit and for cruel bondage.
The Lord (to Moses): Go in and speak to Pharaoh king of Egypt, that he let the children of Israel go out of his land.
Moses (to the Lord): Behold, the children of Israel have not listened to me; how then shall Pharaoh hear me, who am of uncircumcised lips?
The Lord spoke to Moses and to Aaron and gave them a charge to the children of Israel and to Pharaoh king of Egypt, to bring the children of Israel out of the land of Egypt.
These be the heads of their fathers’ houses:
The sons of Reuben the firstborn of Israel; Hanoch, and Pallu, Hezron, and Carmi: these be the families of Reuben.
And the sons of Simeon; Jemuel, and Jamin, and Ohad, and Jachin, and Zohar, and Shaul the son of a Canaanite woman: these are the families of Simeon.
Reuben and Simeon seem only to be mentioned to establish the placement of Levi in the family of Jacob/Israel. (Benson Commentary) Levi is the third son of Israel.
And these are the names of the sons of Levi according to their generations;
Gershon, and Kohath, and Merari: and the years of the life of Levi were 137 years. Their sister was Jochebed. (vs 20)
The sons of Gershon; Libni, and Shimi, according to their families.
And the sons of Kohath; Amram, and Izhar, and Hebron, and Uzziel: and the years of the life of Kohath were 133 years.
And the sons of Merari; Mahali and Mushi: these are the families of Levi according to their generations.
And Amram took him Jochebed his father’s sister to wife; and she bore him Aaron and Moses: and the years of the life of Amram were 137 years.
And the sons of Izhar; Korah, and Nepheg, and Zichri.
And the sons of Uzziel; Mishael, and Elzaphan, and Zithri.
And Aaron took him Elisheba, daughter of Amminadab, sister of Naashon, to wife; and she bore him Nadab, and Abihu, Eleazar, and Ithamar.
And the sons of Korah; Assir, and Elkanah, and Abiasaph: these are the families of the Korhites.
And Eleazar Aaron’s son took him one of the daughters of Putiel to wife; and she bore him Phinehas: these are the heads of the fathers of the Levites according to their families.
These are that Aaron and Moses, to whom the Lord said, Bring out the children of Israel from the land of Egypt according to their armies.
These are they which spoke to Pharaoh king of Egypt, to bring out the children of Israel from Egypt: these are that Moses and Aaron.
And it came to pass on the day when the Lord spoke to Moses in the land of Egypt, That the Lord spoke to Moses, saying, I am the Lord: speak to Pharaoh king of Egypt all that I say to you. And Moses said before the Lord, Behold, I am of uncircumcised lips, and how shall Pharaoh listen to me?
The genealogy ends with the two great patriots, Moses and Aaron, and comes in the Bible at this point to show that they were Israelites, bone of the bone, and flesh of the flesh of those whom they were sent to deliver; raised up to them of their brethren, as Christ also would be, who was to be the Prophet and Priest, the Redeemer and Lawgiver of the house of Israel, and whose genealogy also, like this, was carefully preserved. (Benson Commentary)