What does Malachi 3:5 mean?
Malachi 2:17 records Israel's arrogant and hypocritical question thrown at God: "Where is the God of justice?" In short, the claim is that God is not doing enough to punish the wicked. Of course, what Israel has in mind is other nations, and other cultures, and other people. God's response here, in verse 5, is "be careful what you wish for." Asking God to deal with sin in the world means asking God to deal with the sin in us, and our own lives, first and foremost.God's judgment will not be somewhere far away, or aimed at other nations, leaving Israel untouched. On the contrary, His judgment will begin with Israel: He will "draw near" for judgment. The sins listed in this verse can all be found condemned in the Law of Moses.
Though this book, and these words, are specifically directed at the nation of Israel, there are principles which can be applied to modern Christians. First, we need to consider our own sins before we demand that God judge the sins of others (Matthew 7:3–5). Likewise, before God's people can expect to honor Him, and serve Him, we need to experience purification. Suffering and persecution may be God's ways of "refining" His church in preparation for what lies ahead.