Lehi’s lineage as a descendant of Manasseh is partial fulfillment of a promise to Joseph of old. Shortly before his death, Joseph of Egypt related assurances that the Lord made unto him concerning his posterity:
“I have obtained a promise of the Lord, that … the Lord God will raise up a righteous branch out of my loins. …
“And it shall come to pass that they shall be scattered again; and a branch shall be broken off, and shall be carried into a far country; nevertheless they shall be remembered in the covenants of the Lord, when the Messiah cometh. …
“Thus saith the Lord God of my fathers unto me. …
“Wherefore the fruit of thy loins shall write, and the fruit of the loins of Judah shall write; and that which shall be written by the fruit of thy loins, and also that which shall be written by the fruit of the loins of Judah, shall grow together unto the confounding of false doctrines, and laying down of contentions, and establishing peace among the fruit of thy loins, and bringing them to a knowledge of their fathers in the latter days; and also to the knowledge of my covenants, saith the Lord” (JST, Genesis 50:24–25, 27, 31; see also 2 Nephi 3:5, 12).
Prior to their flight into the wilderness, Lehi and Ishmael, both descendants of Joseph, lived with their families in Jerusalem, which was part of the kingdom of Judah. One writer suggested an explanation for why Lehi’s ancestry, though descended from Joseph, lived in Jerusalem, which for the most part was made up of descendants of Judah: “Some students of the Book of Mormon have wondered how descendants of Joseph were still living in Jerusalem in 600 B.C. when most members of the tribes of Ephraim and Manasseh were taken into captivity by the Assyrians about 721 B.C. A scripture in 2 Chronicles may provide a clue to this problem. This account mentions that in about 941 B.C. Asa, the king of the land, gathered together at Jerusalem all of Judah and Benjamin ‘and the strangers with them out of Ephraim and Manasseh.’ (2 Chronicles 15:9.) These ‘strangers … out of Ephraim and Manasseh’ who were gathered to Jerusalem in approximately 941 B.C. may have included the forefathers of Lehi and Ishmael” (Daniel H. Ludlow, A Companion to Your Study of the Book of Mormon [1976], 199).