The righteous will be purified, but the wicked will be punished. The list of particular types of people against whom the Lord will judge includes those who are representatives of false Gods (sorcerers), those who violate God’s Law (adulterers, false swearers), and those who are deficient in their proper relationships with their fellow man (those that oppress the wage-earner, those who oppress the widows and fatherless, and those who do not show hospitality to strangers.)
It is interesting how this particular list echoes the themes of the Sermon on the Mount. There is the set of people who do not properly follow the law, and those whose interpersonal relationships require improvement. Since the Bountiful Saints would have heard that information on the previous day, it is probable that they saw some correlation between Malachi’s list and the sermon they had so recently heard.