10 And the God of our fathers, who were led out of Egypt, out of bondage, and also were preserved in the wilderness by him, yea, the God of Abraham, and of Isaac, and the God of Jacob, yieldeth himself, according to the words of the angel, as a man, into the hands of wicked men, to be lifted up, according to the words of Zenock, and to be crucified, according to the words of Neum, and to be buried in a sepulchre, according to the words of Zenos,
The same God who led them out of bondage, preserved them in the wilderness, and sent prophets to testify of him willingly gives himself up as a man to those same people, who have long since forgotten him and turned to their own ways. When he comes, they reject him and crucify him (for committing blasphemy by claiming to be the Messiah).
To underscore his point, Nephi references three Israelite prophets who had testified of these things. We of course have no direct knowledge of these prophets because their words have been removed from the record (too plain and precious, perhaps?).
Is it ironic that critics contend with Nephi's reference to the prophecies of ancient prophets about the sacrifice of Jesus Christ because we don't have their words outside of the Book of Mormon, in light of the fact that the reason we don't have their words is that they were removed by wicked men? Probably.