3:13-16 Your Words Have Been Harsh Against Me
Throughout the book of Malachi, the prophet has uncovered the pretense of religiosity amongst the Jews that covered their hard hearts. The Jews did not realize that their disbelief was speaking louder than their surface obedience.
3:16-18 They Shall Be Mine
This confrontation of the sin of the Jews was effective. Many of these people truly feared the Lord, despite their sinful behavior, and repented. And the Lord listened carefully to this and recorded it in his book of remembrance. They returned their focus to the Lord (meditating on his name), worshipping him. And he took them as his treasure and put his blessing on them.
4:1-3 A Day Is Coming
The Day of the Lord is foretold throughout Scripture. There have been many mini-days of the Lord throughout world history. But the destruction of Jerusalem in 70 AD was the culmination of all of them. Here Malachi describes both the judgment and the vindication that this day will bring.
4:4-6 Elijah Is Coming
The book of Malachi is the New Testament in miniature. God sends his prophet to confront the sin of the people and to preach the forgiveness of sins. Some hear the prophet and repent. Others harden their hearts as the day of judgment comes.
But then again, this is actually our lives in miniature. We live in the church and it is very easy for our hearts to grow hard, all while we walk through the motions of worship. Malachi preaches a warning for hypocrites. But Malachi also preaches a Gospel for hypocrites.
And one of the great blessings of this kind of repentance is the way it restores fathers to sons and sons to fathers. Gods blessings are best on display in successive generations.