According to John Tvedtnes, when Lehi was admonishing his son Joseph, he told him of a prophecy uttered by their ancestor Joseph of Egypt, who had foreseen that the Egyptians would bring the Israelites into bondage. Part of that prophecy spoke of Moses: "And Moses will I [the Lord] raise up, to deliver thy people out of the land of Egypt" (2 Nephi 3:9-10). Joseph further declared: "and I will make a spokesman for him" (2 Nephi 3:17). This prophecy is also found in Genesis 50:29, 34-35 of the Joseph Smith Translation, which adds that the name of the spokesman would be Aaron.
In Targum Pseudo-Jonathan of Genesis 50:24, Joseph tells his family, "Behold you will be enslaved in Egypt, but do not make plans to go up out of Egypt until the time that TWO deliverers come and say to you, "The Lord surely remembers you." (emphasis added) This suggests that Joseph knew about the coming of Moses and Aaron to liberate Israel and confirms Joseph Smith's addition to that very place in the Genesis account.
Though the Jewish tradition regarding Joseph of Egypt's prophecy about Moses and Aaron can be traced to the second century A.D., the relevant texts were not available to Joseph Smith. The existence of that prophecy in both the Book of Mormon and the Joseph Smith Translation of Genesis provides evidence for the historicity of the account. [John Tvedtnes, "Joseph's Prophecy of Moses and Aaron" in Insights, Vol. 21, No. 1, 2001]