This Bible contradiction is from the Skeptic's Annotated Bible.
Acts 7:22 View context
And Moses was learned in all the wisdom of the Egyptians, and was mighty in words and in deeds.
Exodus 4:10-16 View context
And Moses said unto the LORD, O my Lord, I [am] not eloquent, neither heretofore, nor since thou hast spoken unto thy servant: but I [am] slow of speech, and of a slow tongue.
And the LORD said unto him, Who hath made man's mouth? or who maketh the dumb, or deaf, or the seeing, or the blind? have not I the LORD?
Now therefore go, and I will be with thy mouth, and teach thee what thou shalt say.
And he said, O my Lord, send, I pray thee, by the hand [of him whom] thou wilt send.
And the anger of the LORD was kindled against Moses, and he said, [Is] not Aaron the Levite thy brother? I know that he can speak well. And also, behold, he cometh forth to meet thee: and when he seeth thee, he will be glad in his heart.
And thou shalt speak unto him, and put words in his mouth: and I will be with thy mouth, and with his mouth, and will teach you what ye shall do.
And he shall be thy spokesman unto the people: and he shall be, [even] he shall be to thee instead of a mouth, and thou shalt be to him instead of God.
Exodus 6:12-30 View context
And Moses spake before the LORD, saying, Behold, the children of Israel have not hearkened unto me; how then shall Pharaoh hear me, who [am] of uncircumcised lips?
And the LORD spake unto Moses and unto Aaron, and gave them a charge unto the children of Israel, and unto 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 Canaanitish woman: these [are] the families of Simeon.
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] an hundred thirty and seven years.
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] an hundred thirty and three 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 bare him Aaron and Moses: and the years of the life of Amram [were] an hundred and thirty and seven 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 bare 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 bare 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 spake 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 spake unto Moses in the land of Egypt,
That the LORD spake unto Moses, saying, I [am] the LORD: speak thou unto Pharaoh king of Egypt all that I say unto thee.
And Moses said before the LORD, Behold, I [am] of uncircumcised lips, and how shall Pharaoh hearken unto me?