Joseph Smith claimed Moroni quoted Malachi 4:5 in 1823 as such,
“Behold, I will reveal unto you the Priesthood, by the hand of Elijah the prophet: before the coming of the great and dreadful day of the Lord.”
~JS History of the Church 1:12~
The actual verse reads,
“Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the Lord.”
This represents a significant event in both Church History and biblical alteration. Joseph did not include these angelic changes in his revised ‘Inspired Version’ of the Bible.