In 2 Nephi 3:10 Lehi recounts a prophecy by Joseph of Egypt. Joseph heard the word of the Lord saying:
And Moses will I raise up, to deliver thy people out of the land of Egypt.
Here Lehi claims Joseph knows about the Israelites bondage in Egypt and how they would be delivered by Moses and Aaron, however this is not found in the Bible.
Interestingly John Tvedtnes notes two second century translations of the Bible in Aramaic which confirm Joseph’s prophecy of Moses. These documents were not available to Joseph Smith yet they agree with that Book of Mormon.
How would Joseph have known about this?