In our study of Malachi chapter three, we will look at the two messengers that were to come and the message that they were to bring.
"'See I will send my messenger, who will prepare the way before me. Then suddenly the Lord you are seeking will come to his temple; the messenger of the covenant, whom you desire, will come,' says the Lord Almighty." NIV translation
The first part of this verse is quoted in all of the gospels and refers to the coming of John the Baptist. We know that it is John the Baptist because all of them use that description of him.
The second part refers to the coming of Jesus not as a sacrifice but as the "God of justice" that the people asked for at the end of chapter two.
Jesus came the first time in the form of a baby to be the prefect payment for our sins. Therefore, we know that this speaks of Jesus' return as the judge as recorded by John in Revelation.
"But who can endure the day of his coming? Who can stand when he appears? For he will be like a refiner's fire or a launderer's soap." NIV translation
This verse speaks to the purpose for Jesus' return and that is to make His people pure by removing all of the effects of sin. The purpose of a "refiner's fire or a launderer's soap" is the same and that is to make something pure/clean. In order to make something pure, someone has to determine what is impure (Judge) and provide a means for its removal.
"He will sit as a refiner and purifier of silver, he will purify the Levites and refine them like gold and silver. Then the Lord will have men who will bring offerings in righteousness, and the offerings of Judah and Jerusalem will be acceptable to the Lord, as in days gone by, as in former years." NIV translation
This passage refers to the thousand year reign as recorded by John in Revelation 20. Those that have been purified by the tribulation (fire) and given their lives (offerings in righteousness) will be resurrected to reign with Jesus for this period.