3rd Nephi 24:1-3
And it came to pass that he commanded them that they should write the words which the Father had given unto Malachi, which he should tell unto them. And it came to pass that after they were written he expounded them. And these are the words which he did tell unto them, saying: Thus said the Father unto Malachi—Behold, I will send my messenger, and he shall prepare the way before me, and the Lord whom ye seek shall suddenly come to his temple, even the messenger of the covenant, whom ye delight in; behold, he shall come, saith the Lord of hosts. But who may abide the day of his coming, and who shall stand when he appeareth? For he is like a refiner’s fire, and like fuller’s soap. And he shall sit as a refiner and purifier of silver; and he shall purify the sons of Levi, and purge them as gold and silver, that they may offer unto the Lord an offering in righteousness.
Christ is telling us about the messenger that will come and prepare this world for his second coming. Only through the messenger will we be able put ourselves into a position for the return of Christ. We can be thankful that this messenger does come and will return with instructions from Christ to his Church.