The reason for sorcery, adultery, false witness, and other transgressions of God’s Law is a lack of the fear of God. Never hesitate to preach the fear of God. It causes sinners to depart from sin (see Prov. 16:6). Preach the thunderings and lightnings of Mount Sinai and preach future punishment!
The preaching of the Law without retribution will not be effective in winning souls for Christ. It has been well said that God’s Law without consequence is nothing but good advice. The world will agree with “You shall not kill.” That makes sense. They will smile at “You shall not commit adultery.” They know it destroys families. They will give assent to “You shall not bear false witness.” They know that it harms friendships. The Ten Commandments certainly are good advice. However, when you preach the Law with the message that God “will judge the world in righteousness” (as Paul preached in Athens; see Acts 17:22–31), your listeners may be provoked to say, “We will hear you again on this matter” (Acts 17:32). And sinners will be soundly saved.
Malachi 3:5 And I will come near you for judgment;
I will be a swift witness
Against sorcerers,
Against adulterers,
Against perjurers,
Against those who exploit wage earners and widows and orphans,
And against those who turn away an alien—
Because they do not fear Me,”
Says the Lord of hosts.
Ray Comfort's Daily Evidence 