Come Out From Among Them and Be Separate!
God's purpose was to bring Israel into the Land of Promise—and He would do just that. But the land was filled with people who practiced abominable wickedness. Because Israel was a carnal people, not having the Holy Spirit, and because they had been raised in an oppressive pagan culture, they would be tempted to syncretize and "borrow" pagan elements in their worship of God. This, of course, was completely unacceptable to God.
One of the practices of the people of Canaan was child sacrifice. Children, most often the firstborn, were burned alive to the false god Molech in the belief that their innocence and sinlessness would appease him and make the prayers the children supposedly brought before him more acceptable (hence the mention of mediums and familiar spirits, which were other forms of communication with a god). While it may seem incredible to us that anyone could be seduced into such horrific practice, Israel would not have found it unthinkable—it was simply one of many religious practices of the day. God, however, found it utterly loathsome! So, He unambiguously condemns child sacrifice in the first seven verses of the chapter. The penalty for such conduct was death, and the executioners were to be the people, not the state. This crime was so appalling that God wanted the entire community involved in its eradication. And notice, God directly connects holiness and sanctification not with such abhorrent practices, but with conscientious obedience to His laws.
This chapter also contains a repetition of the laws of sexual morality, albeit in a condensed form. The laws regarding sexual relations are repeated, but the emphasis is on the punishment and the enormity of the crime. Once again, notice the connection between sin and the defilement of the land.
Notice also that the dietary laws of clean and unclean meats are mentioned and specifically connected to holiness—that is, separation from the people of the surrounding lands. The dietary laws, too, were given primarily for holiness purposes rather than physical health. Indeed, the dietary laws do have many health benefits, and no doubt God so intended them; but their primary purpose is stated as being for holiness. By creating such dietary laws, God added a dimension to daily living that constantly reminded the Israelites that they were to continue to be separate from the people of the world, and the laws created a significant frustration to fellowship with non-Israelites. Does God want such a distinct separation between Christians and the world? Yes! Notice what the apostle Paul wrote: "And what agreement has the temple of God with idols? For you are the temple of the living God. As God has said: 'I will dwell in them and walk among them. I will be their God, and they shall be My people.' Therefore, 'Come out from among them and be separate, says the Lord. Do not touch what is unclean, and I will receive you. I will be a Father to you, and you shall be My sons and daughters, says the Lord Almighty'" (2 Corinthians 6:16-18 2 Corinthians 6:16-18  And what agreement has the temple of God with idols? for you are the temple of the living God; as God has said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people.
 Why come out from among them, and be you separate, said the Lord, and touch not the unclean thing; and I will receive you.
 And will be a Father to you, and you shall be my sons and daughters, said the Lord Almighty.
American King James Version×).