Previous prophets had spoken of the coming King. Malachi spoke of a coming messenger who would prepare the way for that King. He was described as Elijah. Jesus referred to John the Baptist as Elijah, the one who prepared His way (Mt. 11:7-15).
The King was also pictured as a Messenger who would purify the sons of Levi as one would refine gold or silver by purifying it of its impurities in a smelter. Today under Christ, all Christians are priests just as the sons of Levi had been. We have been purified through the blood of Christ in baptism.
When pointing out the transgressions of the Jews, they asked the prophet in what ways had they committed those various acts. Their consciences were so seared that they did not recognize sin. In each case, he described their actions that had displeased God. One cannot question God’s love based upon current circumstances. Sometimes the wicked seem to be blessed while the righteous suffer. The Lord has remembered the faithful. He made note of them and stated, “They shall be Mine…”