The Savior wanted to be sure that the Nephites had the words of Malachi, so that they could be preserved for future generations. I suspect that these words would be valuable to the next generations as they experienced apostasy and great trials.
In particular, just as with the words of Isaiah, I suspect that the promise of redemption and restoration would have been soothing and comforting.
“17 And they shall be mine, saith the Lord of Hosts, in that day when I make up my jewels; and I will spare them as a man spareth his own son that serveth him.”
The metaphor of the Lord making up his jewels is a beautiful regal one that implies redemption and perfectability. God knows who we are and who we can become.