Application to Israel: The servant will free prisoners—those who are in physical and spiritual bondage. Their spiritual captivity was caused by turning from their God, and they are in physical captivity because they are physically removed from their homeland.
Application to Nephi’s audience: Nephi would see his people as these distant “prisoners” awaiting a redeemer. The darkness refers to both the spiritual state and to their dispersion, which has made them hidden as it were in darkness. Their ultimate reward is to again be in the glory of Yahweh’s presence—in favored places.
Comparison: The King James Version reads “to them that are in darkness” while the Book of Mormon reads “to them that sit in darkness.” Tvedtnes analyzes how “sit” might have been in the original but been deleted through understandable copying errors.