This is basically Malachi chapter 4, an easily accessible text during the time period for which the Book of Mormon was intended.
(I'm talking about the present day!)
But beyond the fact that these six verses are completely superfluous in modern scripture, there is one little confusing thing I'd like to point out. Verse 4:
Remember ye the law of Moses, my servant, which I commanded unto him in Horeb for all Israel, with the statutes and judgments.
This is identical to the Malachi version except that it contains one extra comma. In Malachi's context, this verse makes sense because it was written hundreds of years before the birth of Christ. But in 3 Nephi, Christ is speaking these words to the people with the express purpose of expounding them (see 3 Nephi 24:1).
But it's church doctrine that Christ retired the Mosaic Law—that we're held to a higher law less based on specific rules and more based on following the spirit of God's law (which, of course, doesn't jive with the modern church's take on things like modesty, the Word of Wisdom, etc.). So why would Jesus include verse 4, which reminds us of an obsolete law of Heaven? Wouldn't it be better to skip this verse or to use it as an opportunity to explain the transition away from the Law of Moses?
So much for expounding, Jesus.