We have some familiar verses in this chapter that once again appear in our Christian calendar when we come to Advent and specifically John the Baptist. Look at vs.1 and we hear about the messenger that is being sent ahead of the coming Messiah. Remember the term "my messenger" is literally in Hebrew Malachi. If you read Matthew 11:10 and its corresponding Gospels (Mark 1:2, Luke 1:17,76) we see it referring to John the Baptist.
He then follows up that reference with what God will do when the Messiah comes. The image of a refiner's fire is brought up which is used in relationship to people and how they will be purified before they are able to approach the Lord. Here those who are purified are specifically those who come from the priestly families because all along it was the priests who were turning their back on God. Here is a song that makes me think of a refiner's fire. Oldie but goodie.
Notice once again how God will judge when the Messiah comes. He will bear witness against, he will speak out against and rule against in a negative sense the following: sorcerers, adulterers, those who swear falsely, those who oppress the hired workers in their wages, those who oppress the widow and the orphan, those who oppress the immigrant, those who do not fear the Lord. That's a long list but it is doable if we think about it.
The last part of this chapter is a castigation to those who do not give the full tithe to the Lord. There is a temptation to give what is left over at the end that we think we can afford. I have always said that we are to give our tithe, our 10%, at the beginning and then go from there. It has to be a part of our budget from the very beginning.