This section opens with a preamble in 18:1‚Äď5 and closes with a formal postscript at the close of chapter 20. These are very important because they give the reason for the restrictions and regulations of the social life of His people. We are living in a day when the moral foundations have been broken up and removed. ‚ÄúWho makes the rules, and what is right and wrong?‚ÄĚ asks the sneering skeptic. This preamble and postscript give us an explanation: God demands that His people be holy. Purity in all life's situations is the command of God.