Nephi inserts Isaiah, chapters 48 and 49. There is no original chapter break before their inclusion, but the original does break at the end of the inclusion of Isaiah 49. Our Chapter 20 of 1 Nephi is set off to be more easily compared to Isaiah 48.
Nephi’s expertise with Isaiah is evident in these two chapters. Although they are part of a spontaneous expansion of Nephi’s original plan, they aptly amplify the themes that he has been discussing, about the relationship of Jehovah’s messianic mission and the children of Israel, among whom he would be mortal.
Isaiah sets up the problem in these verses. The house of Jacob, or Israel, has a special covenant with Jehovah, but Israel is not keeping up its part of the covenant. They swear by Jehovah, but not in truth. They call themselves a holy city, but they do not do the actions of those who are holy.
Jehovah has therefore instructed them through prophets, who called them to repentance, but they were obstinate.
Of interest in the first verse is the insertion of “or out of the waters of baptism” as a clarification of the waters of Judah. Joseph Smith entered this as a marginal note, in parenthesis, for the 1840 edition. It was therefore not part of the original dictation, but was Joseph’s later examination of the text.