The Lord warning Nephi, and leading “those who believed in the revelations of God” into the wilderness, is an example of the principle that Nephi recorded earlier. The Lord “leadeth away the righteous into precious lands, and the wicked he destroyeth, and curseth the land unto them for their sakes” (1 Nephi 17:38). Nephi had taught that the Lord would lead the house of Israel out of Egypt. It was also the principle of Lehi and his people being led out of Jerusalem. There are other examples of this principle later in the Book of Mormon.
This is the first time that Nephi’s sisters are mentioned in the Book of Mormon (v. 6). How many sisters he had and how many of them followed him is not mentioned. Some of them had married Ishmaels sons as commented on under 1 Nephi 7:4–5 and learned from the Book of Lehi. That they traveled in the wilderness “for the space of many days” (v. 7) does not help us much geographically, nor is that the purpose of the Lord in giving us the Book of Mormon. The people calling “the place Nephi,” and calling “themselves the people of Nephi” (vv. 8–9) is the birth of the Nephite nation.