In Mosiah 15:24, the existential clause “and there are those who have part in the first resurrection” was changed in the 1837 edition to “and these are those who have part in the first resurrection”. This change may actually be a typo. It was not marked in 𝓟 by Joseph Smith in his editing for the 1837 edition. The two words there and these are visually similar. In addition, the occurrence of “and these are they that have died before Christ came” in the following clause may have led to replacing the preceding there with these.
When the larger passage is considered, we find that Abinadi identifies three groups of people dying prior to Christ’s resurrection who will be resurrected in the first resurrection: namely, (1) the righteous, (2) those who died without the law, and (3) little children (who died innocent of sin):
The use of there for the second group (listed under 2 above) is existential and means that the first resurrection will involve others in addition to the righteous. Note, in particular, that the inappropriate change to these makes verse 24 redundant: verse 22, in referring to the resurrection of the righteous, has already stated that “these shall come forth in the first resurrection”, while verse 24 (from the 1837 edition on) restates the same idea (“and these are those who have part in the first resurrection”). But even more problematic is that the change to these makes verse 24 flatly contradict verse 22 by referring to the righteous as “these are they that have died before Christ came / in their ignorance / not having salvation declared unto them”. The critical text will therefore restore the existential there in Mosiah 15:24, the reading of the earliest text and clearly more appropriate than the current reading.
Summary: Restore the use of the existential there in Mosiah 15:24: “and there are those who have part in the first resurrection and these are they that have died before Christ came / in their ignorance / not having salvation declared unto them”; the there allows Abinadi to introduce a second group of people who will be resurrected in the first resurrection—namely, those who died without the law.