Malachi is the seventeenth Book of Prophecy and the thirty ninth book of the Old Testament.
The Book of Malachi is an oracle: The word of the Lord to Israel through Malachi (1:1). This was God’s warning through Malachi to tell the people to turn back to God. As the final book of the Old Testament closes, the pronouncement of God’s justice and the promise of His restoration through the coming Messiah is ringing in the ears of the Israelites. Four hundred years of silence ensues, ending with a similar message from God’s next prophet, John the Baptist, proclaiming, “Repent, for the kingdom of heaven is near” (Matthew 3:2).
Malachi wrote the words of the Lord to God’s chosen people who had gone astray, especially the priests who had turned from the Lord. Priests were not treating the sacrifices they were to make to God seriously. Animals with blemishes were being sacrificed even though the law demanded animals without defect (Deuteronomy 15:21). The men of Judah were dealing with the wives of their youth treacherously and wondering why God would not accept their sacrifices. Also, people were not tithing as they should have been (Leviticus 27:30, 32). But in spite of the people’s sin and turning away from God, Malachi reiterates God’s love for His people (Malachi 1:1-5) and His promises of a coming Messenger (Malachi 2:17–3:5).
(Note: Description used with permission from www.gotquestions.org)