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.”

Joseph Smith, History, 1838–1856 – volume A-1 (Salt Lake City, UT: JSP, 23 December 1805–30 August 1834), 5.

The actual verse reads,

“Beholde, I will send you Elijah the Prophet, before the comming 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.