The prophecy that Nephi would be their ruler and teacher (v. 19) had been given when the Lord appeared to Nephi in the valley of Lemuel about thirty years before. It was given probably a few weeks after they initially left Jerusalem and Nephi had filled that role since that time. Lehi had recognized Nephi’s being “an instrument in the hands of God, in bringing us forth into the land of promise” (2 Nephi 1:24).
The Lamanites had also been cut off from the presence of the Lord as prophesied (v. 20). This was the real cursing of the Lord (v. 21). Without the guidance of the Lord their iniquities would abound. The withdrawal of the Spirit from them individually would now come upon them collectively. Of course the coming generation would be born with the light of Christ, but it would not help them unless they repented of the ways of their fathers. Thus as Alma says: “they brought upon themselves the curse; and even so doth every man that is cursed bring upon himself his own condemnation” (Alma 3:19).
The skin of blackness (v. 21) should be read as a comparison to the lighter skin of the Nephites and not taken literally. It was brought upon the people to make them loathsome to the people of Nephi. Alma later says it was a mark “that thereby the Lord God might preserve his people, that they might not mix and believe in incorrect traditions which would prove their destruction” (Alma 3:7–8). It is important to distinguish between the curse and the mark. While there are many variations of skin color in the world, they do not specify any degree of righteousness or unrighteousness. The darker skin of the Lamanites was a distinction between a people of the same origin, and the Lord used the mark to keep the righteous separated from the wicked. As one continues to read the Book of Mormon, it will be evident that the Lord continually endeavored to teach the gospel to the Lamanites and bring them out of their wickedness. At times the efforts were very successful. The Nephites who apostatized and joined the Lamanites were cursed and cut off from the presence of the Lord (v. 23), but nothing was said about their being marked. As long as the Lamanites remained in their wicked ways, they were a scourge to stir up the Nephites to remember the Lord (v. 25).