Matthew 7:13–14 (King James Bible) for wide is the gate and broad is the way that leadeth to destruction and many there be which go in thereat because strait is the gate and narrow is the way which leadeth unto life and few there be that find it
Here in verse 13, the 1852 LDS edition changed the relative pronoun that to which; this change, probably accidental, may have been prompted by the which that occurs in the following verse (compare “that leadeth to destruction” in verse 13 with “which leadeth unto life” in verse 14). In any event, the corresponding King James text has that in verse 13 and which in verse 14. The critical text will restore the original that to verse 13.
The relative clause in each of these verses is restrictive, and “strict grammarians” prefer that rather than which in restrictive relative clauses (although in actual usage both occur). If we decided to apply such a “rule” in this passage, we would actually need to change the second which to that rather than the other way around. In any event, both the King James and the Book of Mormon texts show variation between that and which for this passage. On the other hand, the original Greek exhibits the same feminine relative pronoun for each clause (there is no choice in the Greek). For more on the competition between that and which in restrictive relative clauses, see the first two entries under that in Merriam-Webster’s Dictionary of English Usage. Also see the general discussion under which in volume 3 of the critical text.
Summary: Restore the original restrictive relative pronoun that in 3 Nephi 14:13, which makes the text agree with the King James reading; the larger passage has that in verse 13 but which in the parallel sentence in verse 14.