Nephi first explains that his people do not understand Isaiah because Nephi has deliberately withheld cultural information from them about the “manner of the Jews.” This scenario supports the hypothesis of a large indigenous population adopted politically and religiously into the Nephite community. If most of the Nephites had been born in the Old World, then their Jewish acculturation would already have taken place. For children born in the wilderness who lacked learning about “the manner of the Jews,” Lehi, not Nephi, would be responsible.
But Nephi is clearly speaking of how he had educated the current Nephites, not a future uneducated population and not a current younger generation who would have unconsciously picked up much Old World culture from their parents. Rather, Nephi assumes a key role in the transmission of cultural information to a large number of local people being admitted into Nephite society. Nephi is deliberately choosing what cultural information to pass on, not only as king but also as the creator of a new social order based on gospel principles rather than Jewish traditions.
In the second part of the verse, Nephi gives his reason for this selectivity: “for their [the Jews’] works were works of darkness, and their doings were doings of abominations.” His meaning is obscure. Surely he did not condemn his entire heritage, although he certainly has jettisoned some part of it. Perhaps his condemnation is related to Isaiah’s denunciations of faithless Israel, which he has just finished copying. Perhaps he was reacting more personally, because of his father’s rejection by the Jews.
I lean toward Isaiah’s influence because Nephi, rather uncharacteristically for him, phrases his denunciation in two parallel phrases with identical meanings. Typically, he prefers rather plain prose, only rarely creating polished literature like his “psalm” (2 Ne. 4:16–35). I suggest that this paired parallel construction, following immediately after the long and laborious process of copying Isaiah, implies that Nephi’s comments should be seen as his own opinion based on Isaiah’s criticisms.
What does he mean by “works of darkness?” Obviously, he is condemning, not Yahweh’s commandments nor the Mosaic law, but how Jews carried out the law’s provisions. Like Isaiah, Nephi would condemn those who oppressed the poor. However, there is no reason to believe that this is what he had in mind. He links these “works of darkness” with the Jewish “manner of prophesying.” What is the connection?
Although Nephi provides no information, I conjecture that it refers to the Josian reform that altered Jewish religion and against which his father preached. In particular, the Josian reform appears to have had the effect of removing the active teaching of the Atoning Messiah. This coming Messiah is clearly Nephi’s greatest theme, and therefore the removal of that teaching from the Jews’ religion would have been one of the greatest “works of darkness.”